Title of Invention	AN IMPROVED PROCESS FOR SYNTHESIS OF TRANS -ALKENOIC ACIDS.
Abstract	The present invention relates to an improved process for synthesis of trans -alkenoic acids of formula CH3-(CH2) R- CH=CH-(CH2)RiCOOH wherein R is 4 to 9, RI is 8 to 16. The process is high yielding for the synthesis of trans-alkenoic acids particularly trans-tetracos-15-enoic acid, bioactive constituents possessing dose related hepatoprotective activity, which is based on malonate, acetoacetate or cyanoacetate chain extension of bis noralkenoic acids. In this procedure direct reduction of acid to alcohol without using esteriflcation route has been reduced. The use of modified reagents Ph3P-Br2 has resulted in higher yields.

Title of Invention

AN IMPROVED PROCESS FOR SYNTHESIS OF TRANS -ALKENOIC ACIDS.

Abstract

The present invention relates to an improved process for synthesis of trans -alkenoic acids of formula CH3-(CH2) R- CH=CH-(CH2)RiCOOH wherein R is 4 to 9, RI is 8 to 16. The process is high yielding for the synthesis of trans-alkenoic acids particularly trans-tetracos-15-enoic acid, bioactive constituents possessing dose related hepatoprotective activity, which is based on malonate, acetoacetate or cyanoacetate chain extension of bis noralkenoic acids. In this procedure direct reduction of acid to alcohol without using esteriflcation route has been reduced. The use of modified reagents Ph3P-Br2 has resulted in higher yields.

Full Text	The present invention relates to an improved process for the preparation of trans-alkenoic acids. The present invention particularly relates to an improved process for the preparation of trans-alkenoic acids of general formula CH3-(CH2)R-CH=(CH2)Ri CC^H wherein R=4-9 Ri=8-16, and more particularly to /raMs-tetracos-15-enoic acid, bioactive constituents possessing dose related hepatoprotective activity. The acids possess hepatoprotective activity comparable to/better than known formulations. Moreover herbal preparations in use as antihepatotoxic/hepatoprotective ones are unstandardised both from biological and chemical aspects. Here are a few constituents possessing all the promise for use in therapeutics as liver protecting drugs. First report about natural occurrence of an acid of this type viz., fr-aws-tetracos-lS-enoic acid [Wang Huiying, Yu Xuefian, Yi Yuanfen & Ding Jingkai. Yunnan Zhiwu Yanjiu, 1989 11 (1), 60-4 (Ch.)] as a constituent of Jojoba oil ex Simmondsia chinensis seeds (0.62-1.11%) was based on GLC analysis. Both nervonic acid from the brain cerebrosides of cattle & man [Klenk, Z. Physiol Chem. 1925,145,244; 1926,157, 283; 1927,166, 268] & selacholeic acid from shark & ray-liver oils [Tsujimoto, J.Soc. Chem. Ind., Japan 1927, 30, 868] were formulated as cis-tetracos-15-enoic acids.The two identical natural products have been synthesized by malonate chain extension of cw-docos-13-enoic acid [J.B. Hale, W.H. Lycan & Roger Adams. J. Am. Chem. Soc., 1930, 52, 4536; Muller & Benzer, Ber., 1939, 72, 615]. In the process tetracos-15-enoic acid was prepared in six steps i.e., (a) Esterification of erucic yield (yield 93%). (b) Reduction of methylerucate with Na metal in n-butyl alcohol (yield 55%), (c) Conversion of erucyl alcohol to erucyl bromide by the action of PBra (yield 50%) (d) Condensation of erucyl bromide with malonic ester over a period of forty eight hours (yield 78%). (e) Hydrolysis and decarboxylation of irucyl malonic ester to tetracos-15-enoic acid (yield 50%) (f) Isomerization of cis product to trans form (yield 90%), in an overall yield of 9.05%. Another publication [D.G. Bounds, R.P. Linstead & B.C.L. Weedon, Journal of Chemical Society, 1954, 448] reported synthesis of cis & trans-tetracos-15-enoic acid by anodic chain extension of oleic & elaidic acids respectively. In the report electrolysis of oleic & elaidic acids in the presence of excess of methyl hydrogen suberate gave the expected mixture of three products by both symmetrical and unsymmetrical coupling of the two compounds. By distillation and hydrolysis of the unsymmetrical products, mixture of cis & trans-tetracos-15-enoic acids were obtained in 30-35% overall yield. All the reported synthetic procedures for trans-alkenoic acids till date are lengthy, nonspecific i.e., yielding mixture of cis & trans isomers and end up with very poor yields. The main object of the present invention is to provide a synthetic method for the production of trans-alkenoic acids, hepatoprotective constituents of natural origin. Another object is to report an economic high yielding synthesis, where the end product i.e., trans-alkenoic acids are obtained up to 70% in overall yield. In the accompanying specifications general formula of t-alkenoic acid has been described and when R=7 and Ri=13 it represents t-tetracos-15enoic acid. Accordingly the present invention provides an improved process for synthesis of trans - alkenoic acids of formula CH3-(CH2) R- CH=CH-(CH2)RiCOOH wherein R is 4 to 9, RI is 8 to 16 which comprises (i) reducing bis noralkenoic acids as herein described to corresponding alkenol in the presence of metal hydride 40 to 70% by wt in a conventional manner, (ii) reacting alkenol compound obtained above with brominating agent at a temperature in the range of -10 to 25°C for 1 to 4 hrs, recovering bromoalkene by known methods (iii) condensing bromoalkene with carboxylic acid ester 60% by wt. of bromo alkene in presence of alkali metal alkoxide to give dicarbalkoxyalkene, iv) hydrolysing the said dicarbalkoxy alkene to corresponding dicarboxylic acid, (v) decarboxylating by thermal decomposition the dicarboxylic acid obtained above partially to trans- alkenoic acid, vi) purifying the product by crystallization using solvent such as herein described to obtain trans-alkenoic acid, the said process characterized in the steps of direct reduction of bisnoralkenoic acid to alcohol in presence of metal hydride and use of brominating agent. In the embodiment of present invention, an improved and high yielding process for the synthesis of trans-alkenoic acids of general formula CH3-(CH2)R-CH=(CH2)RiCO2CO2H where R=4-9 and RI= 8-16, has been described. > In another embodiment of the present invention the process particularly for trans- tetracos-15-enoic acid has been mentioned. > In yet another embodiment of the present invention trans-tetracos-15-enoic acid has been shown to have dose related hepatoprotective activity. > In yet another embodiment of the present invention the bis noralkenoic acid used may be such as trans-henicos-12-enoic acid, trans-docos-14-enoic acid and trans- icos-12-enoic acid, trans-tetradec-8-enoic acid, trans-docos-13-enoic acid. > In another embodiment the brominating agent used may be such as PBrs, PhaP- Br2 complex. > In yet another embodiment the decarboxylation may be carried out by heating the dicarboxylic acid in a dry state or by heating in wet dimethyl sulphoxide containing NaCl, NaaPC^ or some other simple salt. The present invention provides an improved high yielding process for the synthesis of trans-alkenoic acids particularly trans-tetracos-15-enoic acid, bioactive constituents possessing dose related hepatoprotective activity, which is based on malonate, acetoacetate or cyanoacetate chain extension of bis noralkenoic acids which comprises of: (i) Reduction of bis noralkenoic acids to corresponding alkenol using complex metal hydrides in the presence of catechol and/or an organic acid in ether medium, (ii) Conversion of the alkenol to bromoalkene. (iii) Condensation of the bromoene with dialkyl malonate or ethylacetoacetate or ethyl cyanoacetate in presence of alkali metal alkoxide. (iv) Hydrolysis of 1,1 -dicarbalkoxyalkene or 1 -acetyl-1 -carbalkoxyalkene or 1 -cyano- 1-carbalkoxyalkene to the corresponding dicarboxylic acid, (v) Partial decarboxylation of the dicarboxylic acid to /raws-alkenoic acid . vi) Crystallisation of the final product from an organic solvent having 1-4 C atoms by chilling at subzero temperatures. Complex metal hydride used in step (i) may be chosen from LiAlHj NaBFLt or the like. Organic acid used in step (i) may be chosen from CbCCOOH, FsCCOOH and the like. Ether medium employed in step (i) may be chosen from diethyl ether, tetrahydrofuran, dioxane or methyl cellosolve. Conversion of enol to bromocompound in step (ii) may be carried out with PBrs or PHaP-B complex. Alkyl malonate used in (iii) may be chosen from dimethylmalonate and diethylmalonate, acetoacetate may be ethyl acetoacetate or methyl acetoacetate and cyanoacetate may be ethyl cyanoacetate or methyl cyanoacetate. Alkali metal alkoxide employed in (iii) may be selected from Na/K methoxide and ethoxide. Hydrolysis of diester in step (iv) may be carried out using aqueous or methanolic NaOH or KOH or (CH3)3 COK (1.5M-2.5M). Partial decarboxylation in step (v) is carried out by dry heating of the diacid at 170-200°C in an oil bath or by heating in wet dimethyl sulphoxide containing NaCl, NasPCv or some other simple salt at 120-130°. The solvent employed for crystallization of the final product may be chosen from methanol, ethanol, isopropanol or ethyl acetate. The invention is described with reference to the examples given below which should not, however, be construed to limit the scope of present invention. Example 1 a. Reduction of docos-13-enoic acid to docos-13-enol Lithium Aluminium Hydride (LAH, 6.9g) was suspended in absolute diethyl ether in a three necked R.B. flask provided with a dropping funnel, a reflux condenser and a magnetic stirring paddle. To the stirred suspension (placed in an ice bath), docos-13-enoic acid (50 g) dissolved in absolute diethyl ether (300 mL), was added dropwise, the operation was completed in one hour. The reaction mixture was further stirred for another half an hour at r.t. (22±3°C). The reaction was quenched by adding ethyl acetate (100 mL) and 10% aq. HbSC^ (100 mL). Ether layer was separated, washed with water (5x50 mL) and dried over anhydrous NaaSCV Ether was removed by distillation and reaction product recovered by vacuum distillation (202-203°C, Itorr). The product (43g, 90% yield) was characterized by 'H-NMR. b. Conversion of docos-13-enol to bromodocos-13-ene Docos-13-enol (50 g) was dissolved in dry toluene (160 g) and the solution was placed in a three necked R.B. flask fitted with a reflux condenser and a dropping funnel. The solution was cooled to -15°C (cryostat) and PBr3 (20 g) was added to it dropwise. After the addition, the reaction mixture was heated on a steam bath for four hours (Progress monitored on TLC). Toluene was removed from the reaction mixture by distillation and the residue was dissolved in «-hexane (200 mL), the solution was washed with aq. KOH (20%, 50 mL), aq. NaCl (10%, 50 mL), finally with water and then dried over anhydrous MgSC>4. Hexane was removed by distillation under atmospheric pressure and the product under diminished pressure (203-205°C, 1 torr), yield (55g, 93%). c. Conversion of bromodocos-13-ene to l,l-dicarbalkoxytricos-14-ene Absolute ethanol (15 mL) was taken in a three necked R.B. flask fitted with a dropping funnel and a reflux condenser. Sodium metal (600 mg) was added in ethanol, in small pieces, with constant stirring followed by dropwise addition of diethyl malonate (6g) over fifteen minutes. This was followed by dropwise addition of bromoalkene (lOg). The reaction mixture was refluxed on a steam bath for four hours. Ethanol was removed from the reaction mixture on a rotavapour and to the residue HC1 (1%, 100 mL) was added. The mixture was extracted with diethyl ether (5x100 mL). The ether extract was dried over anhydrous Na2SC>4. The ether extract was concentrated to 50 mL and then filtered through a small column (packed with neutral AUOs) to get l,l-dicarbalkoxytricos-14-ene, yield (llg, 88%). d. Hydrolysis of the l,l-dicarbalkoxytricos-14-ene to l,l-dicarboxytricos-14-ene The enediester (10 g) was suspended in 60% aq. ethanolic KOH (6g, 40 mL) and refluxed on a water bath for one hour. Ethanol was removed from the reaction mixture by distillation and the residual aqueous solution was acidified (pH=3) with 10% aqueous H2SO4 and extracted with CHCb (5x50 mL). The CHC13 extract was dried over anhydrous CaCli and then distilled. The residue on cooling gave l,l-dicarboxytricos-14-ene, a solid mass, yield (8g, 91%). .Thermal decomposition of the l,l-dicarboxytricos-14-ene to /-tetracos-15-enoic acid The diacid (5.5 g) was taken in a R.B. flask (50 mL) and heated at 178° in a Woods metal bath for one hour. The product was recovered by distillation under reduced pressure and the distillate crystallized from methanol by chilling at -20°C, yield (3.92 g, m.p. 61°C, 80%). Example 2 a. Reduction of docos-13-enoic acid to docos-13-enol To a suspension of NaBH4 (0.76 g, 0.01 mole) in dry THF (20 mL), docos-13-enoic acid (3.38 g, 0.01 mole) in dry THF (20 mL) was added. CF3COOH (1.14g. 0.01 mole) was added in 15 minutes at 0°C and stirred for four hours at r.t. (22±3°C). The reaction mixture was quenched with 3N-HC1 (5 mL) and extracted with diethyl ether (3xlOmL). Ether extract was washed with IN-aq. NaOH (2x5 mL), water (2x5 mL), brine (2x5 mL) and dried over anhydrous MgSCv. Ether was removed by distillation and docos-13-enol recovered by vacuum distillation (200-203°C, 1 torr), yield (2.6g, 81%). b. Conversion of docos-13-enol to bromodocos-13-ene To an ice cold solution of enol (1.86g), 5.76 m mole) and pyridine (0.72g, 9.21 mmole) in CH3CN (12 mL), solid Ph3P-Br2 (3.16g, 7.48 mmole) was added over 10 minutes. After stirring at r.t. (22±3°C) for one hour (Progress monitored on TLC), the reaction mixture was washed with water (3x5 mL), dried over anhydrous Na2SC4 and distilled under diminished pressure (203-205°C, 1 torr), to get bromodocos-13-ene (2.18 g, 95%). c. Conversion of bromodocos-13-ene to l,l-dicarbalkoxytricos-14-ene Absolute ethyl alcohol (7.5 mL) was taken in a three necked R.B. flask fitted with a dropping funnel and a reflux condenser. Cleaned Sodium metal (300 mg) was added in ethanol, in small pieces. When whole of the sodium metal was reacted, diethyl malonate (3 g) was added dropwise, with constant stirring over a period of 15 minutes.Following this bromodocos-13-ene (5 g) was added similarly. Reaction mixture was further stirred for four hours. The ethanol was completely removed from the reaction mixture and to the residue HC1 (1%, 50 mL) was added. The mixture was extracted with diethyl ether (5x50 mL). The ether layer was dried over anhydrous MgSCX The ether extract was concentrated to 25 mL and then filtered through a small column (packed with neutral A12O3) to get l,l-dicarbalkoxytricos-14-ene, yield (5.4g, 86%). d. Hydrolysis of the l,l-dicarbalkoxytricos-14-ene to l,l-dicarboxytricos-14-ene The enediester (5 g) was suspended in 60% aq.ethanolic potassium hydroxide (3g, 20 mL) and refluxed on a water bath for 50 minutes.The ethyl alcohol was removed from the reaction mixture by distillation and residual aqueous solution was acidified (pH=3-4) with 10% aqueous sulphuric acid and extracted with CHCls (5x25 mL). The chloroform extract was dried over anhydrous CaCk and then distilled. The residue on cooling gave 1,1- dicarboxytricos-14-ene, yield (3.9g, 89%). e. Thermal decomposition of the l,l-dicarboxytricos-14-ene to Metracos-15-enoic acid The diacid (2.75 g) was taken in a R.B. flask (25 mL) and heated at 178° in a Woods metal bath for one hour. The product was recovered by distillation under reduced pressure and the distillate crystallized from methanol by chilling at -25°C yield (1.9g, m.p.61°C, 79%). Example 3 a. Reduction of tetradec-8-enoic acid to tetradec-8-enol To a suspension ofNaBH4(0.38g, 0.005 mole) in dry methyl cellosolve (15 mL), tetradec-8-enoic acid (1 13g, 0.005 mole) in dry methyl cellosolve (15 mL) was added. CF3COOH(0.57g, 0.005 mole) was added in 10 minutes at 0°C and stirred for 3 hours at r.t. (22+3°C). 2N-HC1 (4.0mL) was added to quench the reaction. The quenched reaction mixture was extracted with diethyl ether (2xlOmL). Ether extract was washed with 1N-aq. NaOH (1x5 mL), water (1x5 mL), brine (1x5 mL) and dried over anhydrous MgSO4. Ether was removed by distillation and the product recovered by distillation under diminished pressure (180-185°C, 1 torr), to yield tetradec-8-enol (0.9858, 93%). b. Conversion of tetradec-8-enol to bromotetradec-8-ene A mixture of the tetradec-8-enol (0.61 g), pyridine (0.36g, 4.60 mmole) in GHsCN (8 mL) was cooled in an ice bath and solid PHsP-Bra complex (1.60g, 3.75 mmole) was added over 20 minutes. The reaction mixture was stirred at r.t. (22±3°C) for two hours and washed with water (2x5mL), dried over anhydrous Na2SC4 and subjected to vacuum distillation (178-180°, 1 torr), yield (0.72g, 91%). c. Condensation of bromotetradec-8-ene with dimethyl sodiummalonate Absolute methyl alcohol (10 mL), was placed in a three necked R.B. flask fitted with a dropping funnel and a reflux condenser. Sodium metal (450 mg) was added in methyl alcohol, in small pieces, accompanied by constant stirring. To the clear solution of sodium methoxide, dimethyl malonate (4.2g) was added drop wise over a period of ten minutes. After this bromotetradec-8-ene (6.5g) was added in a similar manner.The reaction mixture was refluxed over a steam bath for two hours. Methyl alcohol was distilled on a rotavapour and the residue was treated with 70 mL of 1% aq. HCI. The mixture was extracted with diethyl ether (3x100 mL). The ether extract was dried over anhydrous Na2S(>4 and concentrated to 50 mL and then filtered through a SiC>2 gel (50 g) column to get l,l-dicarbalkoxypentadec-9-ene, yield (7.01 g, 91%). d. Hydrolysis of the l,l-dicarbalkoxypentadec-9-ene to l,l-dicarboxypentadec-9-ene The enediester (10 g) was suspended in 60% aq. ethanolic KOH (6g, 40 mL) and refluxed on a water bath for one hour. Ethanol was removed from the reaction mixture by distillation and the residual aqueous solution was acidified (pH=3) with 10% aqueous H2SO4 and extracted with CHC13 (5x50 mL). The CHC13 extract was dried over anhydrous CaC\2 and then distilled. The residue on cooling gave l,l-dicarboxypentadec-9-ene, yield (8g, 91%). e. Thermal decomposition of l,l-dicarboxypentadec-9-ene to f-hexadecen-10-oic acid The diacid (5.5 g) was taken in a R.B. flask (50 mL) and heated at 178° in a Woods metal bath for one hour. The product was recovered by distillation under reduced pressure and the distillate crystallized from methanol by chilling at -20°C, yield (3.92 g, m.p. 61°C, 80%). Pharmacological activity /-Tetracos-15-enoic acid (TCA) has been evaluated for antihepatotoxicity/hepato-protective activity both on prophylactic and curative aspects in vivo using CC14, Paracetamol, Galactosamine and alcohol as hepatotoxins employing silymarin as positive standard. In almost all the aspects TCA has shown better protection and reversal of biochemical parameters better then those obtained with silymarin (Tables 1 to 9). Table 1: Hexobarbitone sleep time and zoxazolamine paralysis time (in vivo) of trans- Tetracos-15 enoic acid (TCA) fed at 1 h before CCLt ( 50 ul. kg"1, p.o.) administration in mice8 (Table Removed) a: Values represent the mean ± SE of six animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and CCLt, "C" is mean value of CCLt alone and "V" is the mean value of vehicle treated animals. b: Difference in relation to vehicle treated control group, c: Difference in relation to CCLt control group. p value 0.01 (Dunnetf s t - test). Table 2 : Hepatoprotective activity (in vivo) of trans- Tetracos-15 enoic acid (TCA) (prophylactic study) fed at 48h, 24h, 2h before and 6h after CCLt (0.5ml. kg'1, p.o.) induced hepatic injury in rats". (Table Removed) a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of six animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and CCLt, "C" is mean value of CCLt alone and "V" is the mean value of vehicle treated animals. Unit: each unit is umole pyruvate/min/L. b: is \i mole of/7-nitrophenol formed/min/ L, p value .0.05; 0.01 N S > 0.05 (Dunnetf s t - test). Table 3 : Hepatoprotective activity (in vivo) trans- Tetracos-15 enoic acid (TCA) (curative study) fed at 6h, 24h, 48h after CCU (0.5 ml. kg"1, p. o.) induced hepatic injury in rats8. (Table Removed) a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of eight animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and CCU, "C" is mean value of CCU alone and "V" is the mean value of vehicle treated animals. Unit: each unit is umole pyruvate/min/L. b: is \i mole of /7-nitrophenol formed/min/ L, p value.0.05; 0.01 N S 0.05 (Dunnetfs t - test). Table 4 : Hepatoprotective activity (in vivo) of trans- Tetracos-15 enoic acid (TCA) (prophylactic study) fed at 72 h, 48 h, 24 h, Ih before inhalation of diethyl-ether and 1 h after acetaminophen (APAP) (200. mg. kg"1, i. p., 6 h after exposure to diethyl-ether) hi mice3. (Table Removed) a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of eight animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and "APAP" C" is mean value of APAP alone and "V" is the mean value of vehicle treated animals. Unit: each unit is umole pyruvate/min/L. b: is u mole of /7-nitrophenol formed/min/ L, p value .0.05; 0.01 N S 0.05 (Dunnetf s t - test). Table 5 : Hepatoprotective activity (in vivo) trans- Tetracos-15 enoic acid (TCA) (curative study) fed at 1 h, 24 h, 48 h, 72h after acetaminophen (APAP) (200. mg. kg'1, i. p. 6 h after exposure to diethyl-ether) in mice8. (Table Removed) a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of eight animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and "APAP" C" is mean value of APAP alone and "V" is the mean value of vehicle treated animals. Unit: each unit is pinole pyruvate/min/L. b: is p. mole of /Miitrophenol formed/min/ L, p value .0.05; 0.01 NS 0.05 (Dunnett'st- test). Table 6 : Hepatoprotective activity (in vivo) of trans- Tetracos-15 enoic acid (TCA) (prophylactic study) fed at 72h, 48 h, 24h, 2 h before and 6 h after D- Galactosaniine (GalN) 300. mg. kg"1, s.c.) induced hepatic injury in rats". (Table Removed) a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of six animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and GalN, "C" is mean value of GalN alone and "V" is the mean value of vehicle treated animals. Unit: each unit is umole pyruvate/min/L. b: is \|a mole ofp-nitrophenol formed/min/ L, p value .0.05; 0.01 N S 0.05 (Dunnerfst- test). Table 7 : Hepatoprotective activity (in vivo) trans- Tetracos-15 enoic acid (TCA) (curative study) fed at 6 h, 24 h, 48 h and 72h after D- Galactosamine (GaIN) (300. mg. kg'1, s.c.) induced hepatic injury in ratsa. (Table Removed) a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of six animals hi each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and GaIN, "C" is mean value of GaIN alone and "V" is the mean value of vehicle treated animals. Unit: each unit is umole pyruvate/min/L. b: is ja mole ofp-nitrophenol formed/min/ L, p value .0.05; 0.01 N S 0.05 (Dunnetfst -test). Table 8 : Hepatoprotective activity (in vivo) of frans-Tetracos-lS enoic acid (TCA) against alcohol induced hepatic damage in ratsa. (Table Removed) a: Values represent the mean ± SE of six animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and Alcohol "C" is mean value of Alcohol alone and "V" is the mean value of vehicle treated animals. 1: each unit is umole pyruvate/min/L, 2: is \i mole p-nitroaniline formed/min, b: is \|i mole />-nitrophenol formed/min/ L, p value * Table 9 : Hepatoprotective activity (in vivo) trans- Tetracos-15 enoic acid (TCA) against alcohol induced hepatic damage in rats". (Table Removed) a: Values represent the mean ± SE of six animals hi each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and Alcohol "C" is mean value of Alcohol alone and "V" is the mean value of vehicle treated animals. 3: is n mole K3Fe(CN)6 utilised/mm, 4: is u, mole phosphate formed /min, 5: Represents only change and not protection. p value .0.05; 0.01 (Student's t - test), and others are not significant. Advantages of the synthetic procedure over the earlier ones: a). The number of steps have been reduced, one such step being direct reduction of acid to alcohol without using esterification route, b). Use of modified reagents viz., PhsP-B^ in place of PBrs has resulted in higher yields, c). Even in malonate condensation and hydrolysis steps, reaction time has been appreciably reduced, e). The product obtained is mainly the desired trans isomer, which could be attributed to thermodynamic control, f). The procedure can be effectively and economically employed for the synthesis of /ram-alkenoic acids from corresponding 6/s-noralkenoic acids. We Claim: 1. An improved process for synthesis of trans - alkenoic acids of formula (CH2) R- CH=CH-(CH2)RiCOOH wherein R is 4 to 9, R, is 8 to 16 which comprises (i) reducing bis noralkenoic acids as herein described to corresponding alkenol in the presence of metal hydride 40 to 70% by wt in a conventional manner, (ii) reacting alkenol compound obtained above with brominating agent at a temperature in the range of-10 to 25°C for 1 to 4 hrs, recovering bromoalkene by known methods (iii) condensing bromoalkene with carboxylic acid ester 60% by wt. of bromo alkene in presence of alkali metal alkoxide to give dicarbalkoxyalkene, iv) hydrolysing the said dicarbalkoxy alkene to corresponding dicarboxylic acid, (v) decarboxylating by thermal decomposition the dicarboxylic acid obtained above partially to trans- alkenoic acid, vi) purifying the product by crystallization using solvent such as herein described to obtain trans-alkenoic acid, the said process characterized in the steps of direct reduction of bisnoralkenoic acid to alcohol in presence of metal hydride and use of brominating agent. 2. An improved process as claimed in claim 1, wherein complex metal hydride used in step (i) is Li AIH4 and NaBILt. 3. An improved process as claimed in claims 1 and 2, wherein the brominating agent used is PBr or Ph3P-Br2 complex. 4. An improved process as claimed in claims 1 to 3, wherein carboxylic acid ester employed in step (iii) is alkyl malonate selected from dimethyl sodium malonate and diethyl sodium malonate, ethyl cyanoacetate, methyl cyanoacetate, ethyl acetoacetate, methylacetoacetate. 5. An improved process as claimed in 1 to 4, wherein condensation of bromoalkene with dialkyl sodium malonate is accomplished in 4 hours. 6. An improved process as claimed in claims 1 to 5, wherein hydrolysis in step (iv)_ is carried out using aqueous alcoholic NaOH, KOH or (CHa) C-OK. 7. An improved process as claimed in claims 1 to 6, wherein thermal decomposition in step (v) is carried out using constant temperature bath containing fused Woods metal or oil or by heating with wet dimethyl sulphoxide in presence of NaCl,NO3PO4 8. An improved process as claimed in claims 1 to 7, wherein purification of the product is carried out by crystallizing solvent selected from methanol, ethanol, isopropanol or ethyl acetate. 9. An improved process for the synthesis of trans alkenoic acids substantially as herein described with reference to the examples accompanying these specifications.

Full Text

The present invention relates to an improved process for the preparation of trans-alkenoic acids. The present invention particularly relates to an improved process for the preparation of trans-alkenoic acids of general formula CH3-(CH2)R-CH=(CH2)Ri CC^H wherein R=4-9 Ri=8-16, and more particularly to /raMs-tetracos-15-enoic acid, bioactive constituents possessing dose related hepatoprotective activity.
The acids possess hepatoprotective activity comparable to/better than known formulations. Moreover herbal preparations in use as antihepatotoxic/hepatoprotective ones are unstandardised both from biological and chemical aspects. Here are a few constituents possessing all the promise for use in therapeutics as liver protecting drugs. First report about natural occurrence of an acid of this type viz., fr-aws-tetracos-lS-enoic acid [Wang Huiying, Yu Xuefian, Yi Yuanfen & Ding Jingkai. Yunnan Zhiwu Yanjiu, 1989 11 (1), 60-4 (Ch.)] as a constituent of Jojoba oil ex Simmondsia chinensis seeds (0.62-1.11%) was based on GLC analysis. Both nervonic acid from the brain cerebrosides of cattle & man [Klenk, Z. Physiol Chem. 1925,145,244; 1926,157, 283; 1927,166, 268] & selacholeic acid from shark & ray-liver oils [Tsujimoto, J.Soc. Chem. Ind., Japan 1927, 30, 868] were formulated as cis-tetracos-15-enoic acids.The two identical natural products have been synthesized by malonate chain extension of cw-docos-13-enoic acid [J.B. Hale, W.H. Lycan & Roger Adams. J. Am. Chem. Soc., 1930, 52, 4536; Muller & Benzer, Ber., 1939, 72, 615]. In the process tetracos-15-enoic acid was prepared in six steps i.e., (a) Esterification of erucic yield (yield 93%). (b) Reduction of methylerucate with Na metal in n-butyl alcohol (yield 55%), (c) Conversion of erucyl alcohol to erucyl bromide by the action of PBra (yield 50%) (d) Condensation of erucyl bromide with malonic ester over a period of forty eight hours (yield 78%). (e) Hydrolysis and decarboxylation of irucyl malonic ester to tetracos-15-enoic acid (yield 50%) (f)
Isomerization of cis product to trans form (yield 90%), in an overall yield of 9.05%. Another publication [D.G. Bounds, R.P. Linstead & B.C.L. Weedon, Journal of Chemical Society, 1954, 448] reported synthesis of cis & trans-tetracos-15-enoic acid by anodic chain extension of oleic & elaidic acids respectively. In the report electrolysis of oleic & elaidic acids in the presence of excess of methyl hydrogen suberate gave the expected mixture of three products by both symmetrical and unsymmetrical coupling of the two compounds. By distillation and hydrolysis of the unsymmetrical products, mixture of cis & trans-tetracos-15-enoic acids were obtained in 30-35% overall yield.
All the reported synthetic procedures for trans-alkenoic acids till date are lengthy, nonspecific i.e., yielding mixture of cis & trans isomers and end up with very poor yields.
The main object of the present invention is to provide a synthetic method for the production of trans-alkenoic acids, hepatoprotective constituents of natural origin. Another object is to report an economic high yielding synthesis, where the end product i.e., trans-alkenoic acids are obtained up to 70% in overall yield.
In the accompanying specifications general formula of t-alkenoic acid has been described and when R=7 and Ri=13 it represents t-tetracos-15enoic acid.
Accordingly the present invention provides an improved process for synthesis of trans - alkenoic acids of formula CH3-(CH2) R- CH=CH-(CH2)RiCOOH wherein R is 4 to 9, RI is 8 to 16 which comprises (i) reducing bis noralkenoic acids as herein described to corresponding alkenol in the presence of metal hydride 40 to 70% by wt in a conventional manner, (ii) reacting alkenol compound obtained above with brominating agent at a temperature in the range of -10 to 25°C for 1 to 4 hrs, recovering bromoalkene by known methods (iii) condensing bromoalkene with carboxylic acid ester 60% by wt. of bromo alkene in presence of alkali metal alkoxide to give dicarbalkoxyalkene, iv) hydrolysing the said dicarbalkoxy alkene to corresponding dicarboxylic acid, (v) decarboxylating by thermal decomposition the
dicarboxylic acid obtained above partially to trans- alkenoic acid, vi) purifying the product by crystallization using solvent such as herein described to obtain trans-alkenoic acid, the said process characterized in the steps of direct reduction of bisnoralkenoic acid to alcohol in presence of metal hydride and use of brominating agent.
In the embodiment of present invention, an improved and high yielding process for the synthesis of trans-alkenoic acids of general formula CH3-(CH2)R-CH=(CH2)RiCO2CO2H where R=4-9 and RI= 8-16, has been described.
> In another embodiment of the present invention the process particularly for trans-
tetracos-15-enoic acid has been mentioned.
> In yet another embodiment of the present invention trans-tetracos-15-enoic acid
has been shown to have dose related hepatoprotective activity.
> In yet another embodiment of the present invention the bis noralkenoic acid used
may be such as trans-henicos-12-enoic acid, trans-docos-14-enoic acid and trans-
icos-12-enoic acid, trans-tetradec-8-enoic acid, trans-docos-13-enoic acid.
> In another embodiment the brominating agent used may be such as PBrs, PhaP-
Br2 complex.
> In yet another embodiment the decarboxylation may be carried out by heating the
dicarboxylic acid in a dry state or by heating in wet dimethyl sulphoxide
containing NaCl, NaaPC^ or some other simple salt.
The present invention provides an improved high yielding process for the synthesis of trans-alkenoic acids particularly trans-tetracos-15-enoic acid, bioactive constituents possessing dose related hepatoprotective activity, which is based on malonate, acetoacetate or cyanoacetate chain extension of bis noralkenoic acids which comprises of:
(i) Reduction of bis noralkenoic acids to corresponding alkenol using complex metal
hydrides in the presence of catechol and/or an organic acid in ether medium, (ii) Conversion of the alkenol to bromoalkene. (iii) Condensation of the bromoene with dialkyl malonate or ethylacetoacetate or ethyl
cyanoacetate in presence of alkali metal alkoxide. (iv) Hydrolysis of 1,1 -dicarbalkoxyalkene or 1 -acetyl-1 -carbalkoxyalkene or 1 -cyano-
1-carbalkoxyalkene to the corresponding dicarboxylic acid, (v) Partial decarboxylation of the dicarboxylic acid to /raws-alkenoic acid . vi) Crystallisation of the final product from an organic solvent having 1-4 C atoms by
chilling at subzero temperatures.
Complex metal hydride used in step (i) may be chosen from LiAlHj NaBFLt or the like. Organic acid used in step (i) may be chosen from CbCCOOH, FsCCOOH and the like. Ether medium employed in step (i) may be chosen from diethyl ether, tetrahydrofuran, dioxane or methyl cellosolve. Conversion of enol to bromocompound in step (ii) may be carried out with PBrs or PHaP-B complex. Alkyl malonate used in (iii) may be chosen from dimethylmalonate and diethylmalonate, acetoacetate may be ethyl acetoacetate or methyl acetoacetate and cyanoacetate may be ethyl cyanoacetate or methyl cyanoacetate. Alkali metal alkoxide employed in (iii) may be selected from Na/K methoxide and ethoxide. Hydrolysis of diester in step (iv) may be carried out using aqueous or methanolic NaOH or KOH or (CH3)3 COK (1.5M-2.5M). Partial decarboxylation in step (v) is carried out by dry heating of the diacid at 170-200°C in an oil bath or by heating in wet dimethyl sulphoxide containing NaCl, NasPCv or some other simple salt at 120-130°. The solvent
employed for crystallization of the final product may be chosen from methanol, ethanol,
isopropanol or ethyl acetate.
The invention is described with reference to the examples given below which should not,
however, be construed to limit the scope of present invention.
Example 1
a. Reduction of docos-13-enoic acid to docos-13-enol
Lithium Aluminium Hydride (LAH, 6.9g) was suspended in absolute diethyl ether in a three necked R.B. flask provided with a dropping funnel, a reflux condenser and a magnetic stirring paddle. To the stirred suspension (placed in an ice bath), docos-13-enoic acid (50 g) dissolved in absolute diethyl ether (300 mL), was added dropwise, the operation was completed in one hour. The reaction mixture was further stirred for another half an hour at r.t. (22±3°C). The reaction was quenched by adding ethyl acetate (100 mL) and 10% aq. HbSC^ (100 mL). Ether layer was separated, washed with water (5x50 mL) and dried over anhydrous NaaSCV Ether was removed by distillation and reaction product recovered by vacuum distillation (202-203°C, Itorr). The product (43g, 90% yield) was characterized by 'H-NMR.
b. Conversion of docos-13-enol to bromodocos-13-ene
Docos-13-enol (50 g) was dissolved in dry toluene (160 g) and the solution was placed in a three necked R.B. flask fitted with a reflux condenser and a dropping funnel. The solution was cooled to -15°C (cryostat) and PBr3 (20 g) was added to it dropwise. After the addition, the reaction mixture was heated on a steam bath for four hours (Progress monitored on TLC). Toluene was removed from the reaction mixture by distillation and the residue was dissolved in «-hexane (200 mL), the solution was washed with aq. KOH
(20%, 50 mL), aq. NaCl (10%, 50 mL), finally with water and then dried over anhydrous MgSC>4. Hexane was removed by distillation under atmospheric pressure and the product under diminished pressure (203-205°C, 1 torr), yield (55g, 93%).
c. Conversion of bromodocos-13-ene to l,l-dicarbalkoxytricos-14-ene
Absolute ethanol (15 mL) was taken in a three necked R.B. flask fitted with a dropping funnel and a reflux condenser. Sodium metal (600 mg) was added in ethanol, in small pieces, with constant stirring followed by dropwise addition of diethyl malonate (6g) over fifteen minutes. This was followed by dropwise addition of bromoalkene (lOg). The reaction mixture was refluxed on a steam bath for four hours. Ethanol was removed from the reaction mixture on a rotavapour and to the residue HC1 (1%, 100 mL) was added. The mixture was extracted with diethyl ether (5x100 mL). The ether extract was dried over anhydrous Na2SC>4. The ether extract was concentrated to 50 mL and then filtered through a small column (packed with neutral AUOs) to get l,l-dicarbalkoxytricos-14-ene, yield (llg, 88%).
d. Hydrolysis of the l,l-dicarbalkoxytricos-14-ene to l,l-dicarboxytricos-14-ene
The enediester (10 g) was suspended in 60% aq. ethanolic KOH (6g, 40 mL) and refluxed
on a water bath for one hour. Ethanol was removed from the reaction mixture by
distillation and the residual aqueous solution was acidified (pH=3) with 10% aqueous
H2SO4 and extracted with CHCb (5x50 mL). The CHC13 extract was dried over anhydrous
CaCli and then distilled. The residue on cooling gave l,l-dicarboxytricos-14-ene, a solid
mass, yield (8g, 91%).
.Thermal decomposition of the l,l-dicarboxytricos-14-ene to /-tetracos-15-enoic acid
The diacid (5.5 g) was taken in a R.B. flask (50 mL) and heated at 178° in a Woods metal bath for one hour. The product was recovered by distillation under reduced pressure and the distillate crystallized from methanol by chilling at -20°C, yield (3.92 g, m.p. 61°C, 80%). Example 2
a. Reduction of docos-13-enoic acid to docos-13-enol
To a suspension of NaBH4 (0.76 g, 0.01 mole) in dry THF (20 mL), docos-13-enoic acid (3.38 g, 0.01 mole) in dry THF (20 mL) was added. CF3COOH (1.14g. 0.01 mole) was added in 15 minutes at 0°C and stirred for four hours at r.t. (22±3°C). The reaction mixture was quenched with 3N-HC1 (5 mL) and extracted with diethyl ether (3xlOmL). Ether extract was washed with IN-aq. NaOH (2x5 mL), water (2x5 mL), brine (2x5 mL) and dried over anhydrous MgSCv. Ether was removed by distillation and docos-13-enol recovered by vacuum distillation (200-203°C, 1 torr), yield (2.6g, 81%).
b. Conversion of docos-13-enol to bromodocos-13-ene
To an ice cold solution of enol (1.86g), 5.76 m mole) and pyridine (0.72g, 9.21 mmole) in CH3CN (12 mL), solid Ph3P-Br2 (3.16g, 7.48 mmole) was added over 10 minutes. After stirring at r.t. (22±3°C) for one hour (Progress monitored on TLC), the reaction mixture was washed with water (3x5 mL), dried over anhydrous Na2SC4 and distilled under diminished pressure (203-205°C, 1 torr), to get bromodocos-13-ene (2.18 g, 95%).
c. Conversion of bromodocos-13-ene to l,l-dicarbalkoxytricos-14-ene
Absolute ethyl alcohol (7.5 mL) was taken in a three necked R.B. flask fitted with a dropping funnel and a reflux condenser. Cleaned Sodium metal (300 mg) was added in
ethanol, in small pieces. When whole of the sodium metal was reacted, diethyl malonate (3 g) was added dropwise, with constant stirring over a period of 15 minutes.Following this bromodocos-13-ene (5 g) was added similarly. Reaction mixture was further stirred for four hours. The ethanol was completely removed from the reaction mixture and to the residue HC1 (1%, 50 mL) was added. The mixture was extracted with diethyl ether (5x50 mL). The ether layer was dried over anhydrous MgSCX The ether extract was concentrated to 25 mL and then filtered through a small column (packed with neutral A12O3) to get l,l-dicarbalkoxytricos-14-ene, yield (5.4g, 86%).
d. Hydrolysis of the l,l-dicarbalkoxytricos-14-ene to l,l-dicarboxytricos-14-ene
The enediester (5 g) was suspended in 60% aq.ethanolic potassium hydroxide (3g, 20 mL)
and refluxed on a water bath for 50 minutes.The ethyl alcohol was removed from the
reaction mixture by distillation and residual aqueous solution was acidified (pH=3-4) with
10% aqueous sulphuric acid and extracted with CHCls (5x25 mL). The chloroform extract
was dried over anhydrous CaCk and then distilled. The residue on cooling gave 1,1-
dicarboxytricos-14-ene, yield (3.9g, 89%).
e. Thermal decomposition of the l,l-dicarboxytricos-14-ene to Metracos-15-enoic acid
The diacid (2.75 g) was taken in a R.B. flask (25 mL) and heated at 178° in a Woods metal bath for one hour. The product was recovered by distillation under reduced pressure and the distillate crystallized from methanol by chilling at -25°C yield (1.9g, m.p.61°C, 79%).
Example 3
a. Reduction of tetradec-8-enoic acid to tetradec-8-enol
To a suspension ofNaBH4(0.38g, 0.005 mole) in dry methyl cellosolve (15 mL), tetradec-8-enoic acid (1 13g, 0.005 mole) in dry methyl cellosolve (15 mL) was added. CF3COOH(0.57g, 0.005 mole) was added in 10 minutes at 0°C and stirred for 3 hours at r.t. (22+3°C). 2N-HC1 (4.0mL) was added to quench the reaction. The quenched reaction mixture was extracted with diethyl ether (2xlOmL). Ether extract was washed with 1N-aq. NaOH (1x5 mL), water (1x5 mL), brine (1x5 mL) and dried over anhydrous MgSO4. Ether was removed by distillation and the product recovered by distillation under diminished pressure (180-185°C, 1 torr), to yield tetradec-8-enol (0.9858, 93%).
b. Conversion of tetradec-8-enol to bromotetradec-8-ene
A mixture of the tetradec-8-enol (0.61 g), pyridine (0.36g, 4.60 mmole) in GHsCN (8 mL) was cooled in an ice bath and solid PHsP-Bra complex (1.60g, 3.75 mmole) was added over 20 minutes. The reaction mixture was stirred at r.t. (22±3°C) for two hours and washed with water (2x5mL), dried over anhydrous Na2SC4 and subjected to vacuum distillation (178-180°, 1 torr), yield (0.72g, 91%).
c. Condensation of bromotetradec-8-ene with dimethyl sodiummalonate
Absolute methyl alcohol (10 mL), was placed in a three necked R.B. flask fitted with a dropping funnel and a reflux condenser. Sodium metal (450 mg) was added in methyl alcohol, in small pieces, accompanied by constant stirring. To the clear solution of sodium methoxide, dimethyl malonate (4.2g) was added drop wise over a period of ten minutes. After this bromotetradec-8-ene (6.5g) was added in a similar manner.The reaction mixture was refluxed over a steam bath for two hours. Methyl alcohol was distilled on a
rotavapour and the residue was treated with 70 mL of 1% aq. HCI. The mixture was extracted with diethyl ether (3x100 mL). The ether extract was dried over anhydrous Na2S(>4 and concentrated to 50 mL and then filtered through a SiC>2 gel (50 g) column to get l,l-dicarbalkoxypentadec-9-ene, yield (7.01 g, 91%).
d. Hydrolysis of the l,l-dicarbalkoxypentadec-9-ene to l,l-dicarboxypentadec-9-ene
The enediester (10 g) was suspended in 60% aq. ethanolic KOH (6g, 40 mL) and refluxed on a water bath for one hour. Ethanol was removed from the reaction mixture by distillation and the residual aqueous solution was acidified (pH=3) with 10% aqueous H2SO4 and extracted with CHC13 (5x50 mL). The CHC13 extract was dried over anhydrous CaC\2 and then distilled. The residue on cooling gave l,l-dicarboxypentadec-9-ene, yield (8g, 91%).
e. Thermal decomposition of l,l-dicarboxypentadec-9-ene to f-hexadecen-10-oic acid
The diacid (5.5 g) was taken in a R.B. flask (50 mL) and heated at 178° in a Woods metal
bath for one hour. The product was recovered by distillation under reduced pressure and
the distillate crystallized from methanol by chilling at -20°C, yield (3.92 g, m.p. 61°C,
80%).
Pharmacological activity
/-Tetracos-15-enoic acid (TCA) has been evaluated for antihepatotoxicity/hepato-protective activity both on prophylactic and curative aspects in vivo using CC14, Paracetamol, Galactosamine and alcohol as hepatotoxins employing silymarin as positive standard. In almost all the aspects TCA has shown better protection and reversal of biochemical parameters better then those obtained with silymarin (Tables 1 to 9).
Table 1: Hexobarbitone sleep time and zoxazolamine paralysis time (in vivo) of trans- Tetracos-15 enoic acid (TCA) fed at 1 h before CCLt ( 50 ul. kg"1, p.o.) administration in mice8
(Table Removed)
a: Values represent the mean ± SE of six animals in each group.
H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and CCLt, "C" is mean
value of CCLt alone and "V" is the mean value of vehicle treated animals.
b: Difference in relation to vehicle treated control group, c: Difference in relation to CCLt control group.
p value 0.01 (Dunnetf s t - test).
Table 2 : Hepatoprotective activity (in vivo) of trans- Tetracos-15 enoic acid (TCA) (prophylactic study) fed at 48h, 24h, 2h before and 6h after CCLt (0.5ml. kg'1, p.o.) induced hepatic injury in rats".

(Table Removed)
a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of six animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and CCLt, "C" is mean value of CCLt alone and "V" is the mean value of vehicle treated animals. Unit: each unit is umole pyruvate/min/L. b: is \i mole of/7-nitrophenol formed/min/ L, p value .0.05; 0.01 N S > 0.05 (Dunnetf s t - test).

Table 3 : Hepatoprotective activity (in vivo) trans- Tetracos-15 enoic acid (TCA) (curative study) fed at 6h, 24h, 48h after CCU (0.5 ml. kg"1, p. o.) induced hepatic injury in rats8.

(Table Removed)
a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of eight animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and CCU, "C" is mean value of CCU alone and "V" is the mean value of vehicle treated animals. Unit: each unit is umole pyruvate/min/L. b: is \i mole of /7-nitrophenol formed/min/ L, p value.0.05; 0.01 N S 0.05 (Dunnetfs t - test).
Table 4 : Hepatoprotective activity (in vivo) of trans- Tetracos-15 enoic acid (TCA) (prophylactic study) fed at 72 h, 48 h, 24 h, Ih before inhalation of diethyl-ether and 1 h after acetaminophen (APAP) (200. mg. kg"1, i. p., 6 h after exposure to diethyl-ether) hi mice3.

(Table Removed)
a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of eight animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and "APAP" C" is mean value of APAP alone and "V" is the mean value of vehicle treated animals. Unit: each unit is umole pyruvate/min/L. b: is u mole of /7-nitrophenol formed/min/ L, p value .0.05; 0.01 N S 0.05 (Dunnetf s t - test).
Table 5 : Hepatoprotective activity (in vivo) trans- Tetracos-15 enoic acid (TCA) (curative study) fed at 1 h, 24 h, 48 h, 72h after acetaminophen (APAP) (200. mg. kg'1, i. p. 6 h after exposure to diethyl-ether) in mice8.

(Table Removed)
a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of eight animals in each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and "APAP" C" is mean value of APAP alone and "V" is the mean value of vehicle treated animals. Unit: each unit is pinole pyruvate/min/L. b: is p. mole of /Miitrophenol formed/min/ L, p value .0.05; 0.01 NS 0.05 (Dunnett'st- test).
Table 6 : Hepatoprotective activity (in vivo) of trans- Tetracos-15 enoic acid (TCA) (prophylactic study) fed at 72h, 48 h, 24h, 2 h before and 6 h after D- Galactosaniine (GalN) 300. mg. kg"1, s.c.) induced hepatic injury in rats".

(Table Removed)
a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of six animals in each group.
H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and GalN, "C" is mean
value of GalN alone and "V" is the mean value of vehicle treated animals.
Unit: each unit is umole pyruvate/min/L. b: is |a mole ofp-nitrophenol formed/min/ L,
p value .0.05; 0.01 N S 0.05 (Dunnerfst- test).
Table 7 : Hepatoprotective activity (in vivo) trans- Tetracos-15 enoic acid (TCA) (curative study) fed at 6 h, 24 h, 48 h and 72h after D- Galactosamine (GaIN) (300. mg. kg'1, s.c.) induced hepatic injury in ratsa.

(Table Removed)
a: Values represent the mean ± SE and within parentheses hepatoprotective activity percent mean ± SE of six animals hi each group. H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and GaIN, "C" is mean value of GaIN alone and "V" is the mean value of vehicle treated animals. Unit: each unit is umole pyruvate/min/L. b: is ja mole ofp-nitrophenol formed/min/ L, p value .0.05; 0.01 N S 0.05 (Dunnetfst -test).
Table 8 : Hepatoprotective activity (in vivo) of frans-Tetracos-lS enoic acid (TCA) against alcohol induced hepatic damage in ratsa.

(Table Removed)
a: Values represent the mean ± SE of six animals in each group.
H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and Alcohol "C" is mean
value of Alcohol alone and "V" is the mean value of vehicle treated animals.
1: each unit is umole pyruvate/min/L,
2: is \i mole p-nitroaniline formed/min,
b: is |i mole />-nitrophenol formed/min/ L,
p value * Table 9 : Hepatoprotective activity (in vivo) trans- Tetracos-15 enoic acid (TCA) against alcohol induced hepatic damage in rats".

(Table Removed)
a: Values represent the mean ± SE of six animals hi each group.
H: Hepatoprotective activity was calculated as{l-(T-V/C- V)} x 100 where "T" is mean value of drug and Alcohol
"C" is mean value of Alcohol alone and "V" is the mean value of vehicle treated animals.
3: is n mole K3Fe(CN)6 utilised/mm,
4: is u, mole phosphate formed /min,
5: Represents only change and not protection.
p value .0.05; 0.01 (Student's t - test), and others are not significant.

Advantages of the synthetic procedure over the earlier ones:
a). The number of steps have been reduced, one such step being direct reduction of
acid to alcohol without using esterification route, b). Use of modified reagents viz., PhsP-B^ in place of PBrs has resulted in higher
yields, c). Even in malonate condensation and hydrolysis steps, reaction time has been
appreciably reduced, e). The product obtained is mainly the desired trans isomer, which could be attributed
to thermodynamic control, f). The procedure can be effectively and economically employed for the synthesis of
/ram-alkenoic acids from corresponding 6/s-noralkenoic acids.

We Claim:
1. An improved process for synthesis of trans - alkenoic acids of formula
(CH2) R- CH=CH-(CH2)RiCOOH wherein R is 4 to 9, R, is 8 to 16 which
comprises (i) reducing bis noralkenoic acids as herein described to corresponding
alkenol in the presence of metal hydride 40 to 70% by wt in a conventional
manner, (ii) reacting alkenol compound obtained above with brominating agent at
a temperature in the range of-10 to 25°C for 1 to 4 hrs, recovering bromoalkene
by known methods (iii) condensing bromoalkene with carboxylic acid ester 60%
by wt. of bromo alkene in presence of alkali metal alkoxide to give
dicarbalkoxyalkene, iv) hydrolysing the said dicarbalkoxy alkene to
corresponding dicarboxylic acid, (v) decarboxylating by thermal decomposition
the dicarboxylic acid obtained above partially to trans- alkenoic acid, vi)
purifying the product by crystallization using solvent such as herein described to
obtain trans-alkenoic acid, the said process characterized in the steps of direct
reduction of bisnoralkenoic acid to alcohol in presence of metal hydride and use
of brominating agent.
2. An improved process as claimed in claim 1, wherein complex metal hydride used
in step (i) is Li AIH4 and NaBILt.
3. An improved process as claimed in claims 1 and 2, wherein the brominating agent
used is PBr or Ph3P-Br2 complex.
4. An improved process as claimed in claims 1 to 3, wherein carboxylic acid ester
employed in step (iii) is alkyl malonate selected from dimethyl sodium malonate
and diethyl sodium malonate, ethyl cyanoacetate, methyl cyanoacetate, ethyl
acetoacetate, methylacetoacetate.
5. An improved process as claimed in 1 to 4, wherein condensation of bromoalkene
with dialkyl sodium malonate is accomplished in 4 hours.
6. An improved process as claimed in claims 1 to 5, wherein hydrolysis in step (iv)_
is carried out using aqueous alcoholic NaOH, KOH or (CHa) C-OK.
7. An improved process as claimed in claims 1 to 6, wherein thermal decomposition
in step (v) is carried out using constant temperature bath containing fused Woods
metal or oil or by heating with wet dimethyl sulphoxide in presence of
NaCl,NO3PO4
8. An improved process as claimed in claims 1 to 7, wherein purification of the
product is carried out by crystallizing solvent selected from methanol, ethanol,
isopropanol or ethyl acetate.
9. An improved process for the synthesis of trans alkenoic acids substantially as
herein described with reference to the examples accompanying these
specifications.

Documents:

« Previous Patent

Next Patent »

Patent Number

213233

Indian Patent Application Number

36/DEL/2000

PG Journal Number

01/2008

Publication Date

04-Jan-2008

Grant Date

24-Dec-2007

Date of Filing

18-Jan-2000

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG NEW DELHI -110 001 INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	VISHWA NATH GUPTA	REGIONAL RESEARCH LABORATORY (CSIR)JAMMU, INDIA.
2	VIKRAM BHARDWAJ	RESEARCH LABORATORY (CSIR) JAMMU INDIA
3	BUPINDER SINGH	REGIONAL RESEARCH LABORATORY (CSIR)JAMMU, INDIA.
4	BALKRISHAN CHANDAN	REGIONAL RESEARCH LABORATORY (CSIR)JAMMU, INDIA.
5	KRISHAN AVTAR SURI	REGIONAL RESEARCH LABORATORY (CSIR)JAMMU, INDIA.
6	NARESH KUMAR SATTI	REGIONAL RESEARCH LABORATORY (CSIR)JAMMU, INDIA.
7	OM PARKASH SURI	REGIONAL RESEARCH LABORATORY (CSIR)JAMMU, INDIA.
8	SUKHDEV SWAMI HANDA	REGIONAL RESEARCH LABORATORY (CSIR)JAMMU, INDIA.

PCT International Classification Number

C08F 2/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA