|Title of Invention||
A PROCESS FOR THE SYNTHESIS OF PHARMACOLOGICALLY ACTIVE (Z/E)-GUGGULSTERONES
|Abstract||The invention relates to a process for synthesizing pharmacologically active stereoisomeric mixture of guggulsterones in four steps. The mixture of guggulsterones consists of Z-guggulsterone [4,17(20)-?ra«5-pregnadiene-3,16-dione] and E-guggulsterone [4,17(20)-c/5'-pregnadiene-3,16-dione] and could be in any relative ratio. This improved process comprises (a) reduction of 16-dehydropregnanolone acetate with alkali/alkaline metal borohydride (b) Acid catalysed isomeristion of alcohol with acetic anhydride (c) hydrolysis of acetate with methanolic potassium hydroxide and (d) oxidation of the diol. The active mixture is purified in a known manner.|
Technical field of the invention:
This invention provides a process for the synthesis of pharmacologically active Z/E stereoisomeric mixture of guggulsterones in__high purity^ Guggulsterones consists of a mixture of Z-guggulsterone, [which is 4,17(20)-/ran^-pregnadiene-3,16-dione] and E-guggulsterone, [which is 4,17(20)-c/5"pregnadiene-3,16-dione]. This mixture of stereoisomeric pregnadiene-3,16"diones may be in any relative ratio and is herein after referred as (Z/E)-guggulsterones.
Background of the invention:
Guggul resin obtained from the tree Commiphora mukul belonging to the family Burseraceae is known as guggulu in Sanskrit and guggul in Hindi. This tree is distributed mainly in the States of Gujarat and Rajastan, India. It is cultivated for its oleo-resin, which has wide applications in Allopathic, Ayurvedic and Unani systems of Medicine. The ethyl acetate extract of the resin is an oily resinuous substance and is termed as "Gugulipid", which contains two stereoisomers of guggulsterones. This gugulipid has achieved prominence due to its anti-inflammatory, anti-rheumatic, anti-arthritis, hypo-cholesteremic, hypolipidemic and anti-fertility activities. A cholesterol lowering drug, prepared from guggul-gum/resin of Commiphora mukul is in the market under the trade name 'Guglip'. Medicinal activity of the plant extract is similar to the known drug clofibrate, without its side effects.
Isolation of Z and E-guggulsterones from the oleo-resin or gum of the Commiphora mukul has been reported in the Hterature by Sukh Dev et.al, Tetrahedron, 1972, 28, 2341-52. United States patent specification No.6,086,889 (2000) describes a process for extraction of gugulipid from guggul resin. A process for obtaining pharmacologically active fraction, guggulipid, has also been disclosed in US patent No. 5,273,747 (1993).
However, the tree Commiphora mukul having the biologically active lipid is only available in limited numbers. As such large number of trees are to be harvested for collecting the resin. Further, the naturally occurring resin has only a low concentration of the active guggulsterones. In addition, preparation of dosage forms such as tablets or capsules from the oleo-resin extract poses problems due to its gummy nature. The need for synthesising pharmaceutically potent Z/E guggulsterones of high purity is therefore evident.
A four step precedure for the synthesis of Z and E-guggulsterones was disclosed by Hamied, EP 0447706 (1991). This process includes the reduction of an a, p-unsaturated ketone of 16-dehydropregnenolone acetate (16-DPA) with lithium aluminum hydride in dry tetrahydrofuran. The reagent and the solvent used in this step are expensive and the process is neither cost effective nor used for large scale manufacture.
The objective of this invention is to provide a simple inexpensive process for the production of pharmacologically active synthetic Z/E-guggulsterones. The product obtained has high purity and ratio of Z:E is approximately 80:20.
Disclosure of the invention:
The present invention is a simple process for the synthesis of pharmacologically active synthetic Z/E-guggulsterones in four steps. The process comprises the reduction of 16-dehydropregnenolone acetate with an alkali/alkaline earth metal borohydride in a polar solvent in the presence of a catalyst such as cerium chloride heptahydrate to give 3-acetoxy-5,16-pregnadiene-20-ol. This alcohol is isomerized with acetic anhydride in presence of p-toluenesulfonic acid to give a diastereomeric mixture of diacetyl 5,17(20)-pregnadiene-3,16-diol. Hydrolysis of this diacetate witih a base in the presence of polar solvent gave a mixture of 5,17"(20)-pregnadiene-3,16-diol. Oppeanauer oxidation of the diol mixture in an aromatic solvent in the presence of a catalyst using a hydrogen acceptor produces Z/E-guggulsterones, which is isolated and subjected to further purification. The details of the process are shown in reaction scheme herein below:
The invention relates to a process for synthesizing pharmacologically active Z/E-guggulsterones which comprises reducing 16-dehydropregnanolone acetate with an alkali/alkaline earth metal borohydride in the presence of a known catalyst to give 3-acetoxy-5,16-pregnadiene-20-ol, isomerising said alcohol in the presence of an acid catalyst to produce the corresponding diacetate, hydrolysing said diacetate to produce a diastereromeric mixture of diols and subsequently oxidising said diasteromeric diol mixture with a hydrogen acceptor in the presence of a catalyst to produce Z/E-guggulsterones, isolating and purifying the same from the reaction mixture in a known manner. Individual pure Z-guggulsterone and E-guggulsterone could be obtained by chromatographic separation of Z/E-guggulsterones, followed by crystallization.
This invention also includes a pharmaceutically active Z/E guggulsterones whenever prepared by a process as described herein above.
Purification of the diastereomeric mixture of guggulsterones is carried out by crystallization or by chromatography over a silica gel column using polar and non-polar solvents or mixtures thereof. The polar solvents used for elution are methanol or ethanol and non-polar solvents include petroleum ether, hexane, toluene, chloroform, ethyl acetate or acetone and mixtures thereof.
The following steps illustrate the present invention but do not limit the scope thereof.
Sodium borohydride (21.3 g, 0.56 mol) was added in small portions to a solution of 16-dehydropregnenolone (100 g, 0.28 mol) and cerium (III) chloride heptahydrate (104.7 g, 0.28 mol) in methanol (7.0 L) at 0°C, and stirring was continued for Ih at the same temperature. The reaction mixture was poured into cold water (1.0 L), acidified with dil. HCl and extracted with chloroform. The organic layer was washed with water, 10% sodium bicarbonate, brine and dried over sodium sulfate. The solvent was filtered and evaporated to give 3-acetoxy-5,16-pregnadiene-20-ol (100 g, 99%). Small amount was recrystallized from chloroform-hexane gave as colourless solid, m.p. 146-148°C; IR (KBr) V^ax 3354, 2966, 2934, 1732, 1245, 1043 cm"^ ^H NMR (400 MHz, CDCI3): 5 5.63 (IH, t, J=1.5 Hz, H-16), 5.39 (IH, d, J=5.0 Hz, H-6), 4.56-4.66 (IH, m, H-3), 4.34-4.42 (IH, m, H-20), 2.03 (3H, s, -OCOCH3), 1.36 (2H, d, J=6.5 Hz, H-21), 1.06 (3H, s, -CH3), 0.87 (3H, s, -CH3).
Diacetyl 5,17(20)-pregnadiene-3,16-diol (3)
To a solution of the above alcohol (100 g) in acetic acid (2.25 L) was added acetic anhydride (350 mL) followed by p-toluenesulphonic acid (6.0 g) and the mixture was stirred at for 72 h in N2 atmosphere. The reaction mixture was poured into ice cold
water and extracted with chloroform. The organic layer was washed with water, 10% sodium bicarbonate, brine and dried over sodium sulfate. Filtered and evaporated the solvent to give the rearranged diacetate (110 g, 98%) as semisolid. Small amount was recrytallized from methanol, m.p. 146-148°C; IR (KBr) V„,ax 2943, 2907, 1734, 1375, 1250, 1037 cm"5,17(20)-Pregnadiene-3,16.diol(4)
A solution of diacetate (110 g) in 10% methanolic KOH (250 g in 2.25 L) was refluxed for 6 h. After cooling, the reaction mixture was poured into ice cold water and extracted with chloroform. The organic layer was washed with water, brine and dried over sodium sulfate. Filter and evaporated the solvent to give the diol compound (85 g) as semi solid. Small amount was recrystallized from chloroform-hexane,m.p. 140-142T; IR (KBr) Vn^ax3387, 2935, 2905, 1639, 1373,1054 cm-4,17(20)-Pregnadiene-3,16-dione(5)
A solution of diastereomeric mixture of 5,17(20)-pregnadiene-3,16-diol (85 g) in toluene (5.0 L), cyclohexanone (600 mL) and aluminum isopropoxide (120 g) were refluxed for 4 h. The reaction mixture was cooled, acidified with 10% sulfuric acid (1.0 L) and separated the layer. The aqueous layer was extracted with toluene. The combined toluene layer was washed sequentially, with water, 10% sodium bicarbonate and water. Toluene was distilled off under vaccum to give a gummy residue, which
was chromatographed over silica gel column using mixtures of pet.ether-ethyl acetate for elution to give the Z/E-guggulsterones (32 g, m.p. 176-180°C). The ratio of Z to E in 5 was found to be in the ratio of 85:15 and the purity of guggulsterones is >99% by HPLC.
Obvious alterations and modifications shown to persons skilled in the art are not excluded from the appended claims.
1. A process for synthesizing pharmacologically active Z/E-guggulsterones comprising reduction of 16-dehydropregnanolone acetate with an alkali/alkaline earth metal borohydride in the presence of a known catalyst to give 3-acetoxy-5,16-pregnadiene-20-ol, isomerisation of the said alcohol in the presence of an acid catalyst to produce the corresponding diacetate followed by hydrolysis of the said diacetate to produce a diastereromeric mixture of diols and subsequently oxidising said diasteromeric diol mixture with a hydrogen acceptor in the presence of a catalyst to produce Z/E guggulsterones, isolating and purifying the same from the reaction mixture in a known manner.
2. The process as claimed in claim 1, wherein said alkali/alkaline earth metal borohydride is selected from sodium borohydride.
3. The process as claimed in claims 1 and 2, wherein said reduction of 16-dehydropregnanolone acetate is carried out in a polar solvent selected from methanol, ethanol, isopropyl alcohol, diethyl ether, tetrahydrofuran, dioxan and mixtures thereof.
The process as claimed in claim 1, wherein said reduction is carried out in the presence of a catalyst selected from cerium chloride heptahydrate, zinc chloride, Lewis acids or organic acids like acetic acid.
The process as claimed in claim 1, wherein said isomerization of 3-acetoxy-5,16-pregnadiene-20-ol is carried out in acetic acid and acetic anhydride in the presence of a catalyst.
The process as claimed in claim 5, wherein said catalyst is p-toluene-sulphonic acid.
The process as claimed in claims 1 to 6, wherein said diacetate is hydrolyzed with a base such as sodium or potassium hydroxide in a polar solvent such as methanol, ethanol, isopropyl alcohol and/or mixtures thereof.
The process as claimed in claim 1, wherein said diasteromeric mixture of 55l7(20)-pregnadiene-3,16-diol is oxidized in an aromatic solvent such as toluene or xylene with a hydrogen acceptor in the presence of a catalyst selected from aluminum isopropoxide, aluminum isobutoxide, aluminum phenoxide or aluminum tertiary butoxide.
The process as claimed in claim 8, wherein said hydrogen acceptor is selected from acetone, ethyl methyl ketone, diethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, cycloheptanone, acetophenone benzophenone or l-methyl-4-piperidone.
The process as claimed in any one of the preceding claims 1 to 9, wherein said diastereomeric mixture of guggulsterones is purified by silica gel column chromatography using polar and non polar solvents or mixtures thereof as eluents.
The process as claimed in any one of the preceding claims 1 to 9, wherein said diastereomeric mixture of guggulsterones is purified by steam distillation followed by crystallization.
The process as claimed in claim 10 wherein said polar solvents are selected from methanol, ethanol and said non polar solvents are selected from petroleum ether, hexane, toluene, chloroform, ethyl acetate or acetone and mixtures thereof
Pharmaceutically active Z/E-guggulsterones whenever prepared by a process according to any of the preceding claims.
A process for synthesizing pharmacologically active Z/E-guggulsterones substantially as herein described.
|Indian Patent Application Number||202/CHE/2004|
|PG Journal Number||29/2009|
|Date of Filing||08-Mar-2004|
|Name of Patentee||LAILA IMPEX|
|Applicant Address||40-15-14, BRINDAVAN COLONY, VIJAYAWADA 520 010,|
|PCT International Classification Number||C07J7/00|
|PCT International Application Number||N/A|
|PCT International Filing date|