Title of Invention	PROCESS AND INTERMEDIATE COMPOUNDS USEFUL IN THE PREPARATION OF STATINS, PARTICULARLY ROSUVASTATIN
Abstract	There is provided a process for the preparation of a compound of formula (7) wherein R1 represents an alkyl group; R2 represents an aryl group; R3 represents hydrogen, a protecting group or an alkyl group; and R4 represents hydrogen, a protecting group or a SO2R5 group where R5 is an alkyl group, which comprises a) hydroxylating a compound of formula (1) wherein Y represents a halo group; P1 represents hydrogen or a protecting group, and W represents =O or -OP2, in which P2 represents hydrogen or a protecting group, to give a compound of formula (2), b) oxidising the compound of formula (2) to give a compound of formula (3), c) coupling the compound of formula (3) with a compound of formula (4), wherein R3 represents a protecting group or an alkyl group; R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group; and R6 represents (PR7R8)+X- or P(=O)R7R8 in which X is an anion and R7 and R8 each independently is an alkyl, aryl.

Title of Invention

PROCESS AND INTERMEDIATE COMPOUNDS USEFUL IN THE PREPARATION OF STATINS, PARTICULARLY ROSUVASTATIN

Abstract

There is provided a process for the preparation of a compound of formula (7) wherein R1 represents an alkyl group; R2 represents an aryl group; R3 represents hydrogen, a protecting group or an alkyl group; and R4 represents hydrogen, a protecting group or a SO2R5 group where R5 is an alkyl group, which comprises a) hydroxylating a compound of formula (1) wherein Y represents a halo group; P1 represents hydrogen or a protecting group, and W represents =O or -OP2, in which P2 represents hydrogen or a protecting group, to give a compound of formula (2), b) oxidising the compound of formula (2) to give a compound of formula (3), c) coupling the compound of formula (3) with a compound of formula (4), wherein R3 represents a protecting group or an alkyl group; R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group; and R6 represents (PR7R8)+X- or P(=O)R7R8 in which X is an anion and R7 and R8 each independently is an alkyl, aryl.

Full Text	The present invention concerns a process and intermediate compounds useful in the preparation of statins, particularly Rosuvastatin. According to the present invention, there is provided a process for the preparation of a compound of formula (7): wherein R1 represents an alkyl group, such as a C1-6 alkyl group, and preferably an isopropyl group; R2 represents an aryl group, preferably a 4-fluorophenyl group; R3 represents hydrogen, a protecting group or an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; and R4 represents hydrogen, a protecting group or a SO2R5 group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group, which comprises a) hydroxylating a compound of formula (1): wherein Y represents a halo group, preferably CI or Br; P1 represents hydrogen or a protecting group, and W represents =O or -OP2, in which P2 represents hydrogen or a protecting group, to give a compound of formula (2): b) oxidising the compound of formula (2) to give a compound of formula (3): 1 c) coupling the compound of formula (3) with a compound of formula (4): wherein R3 represents a protecting group or an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; and R6 represents (PR7R8)+X- or P(=O)R7R8 In which X is an anion and R7 and R8 each independently is an alkyl, aryl, alkoxy or aryloxy group, preferably a phenyl group, to give a compound of formula (5): wherein R3 represents a protecting group or an alkyl group, such as a C1-5 alkyl group, and preferably a methyl group; and R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group, d) when W represents -OP2, removing any P2 protecting group and oxidising, the compound of formula (5) to give a compound of formula (6): and e) subjecting the compound of formula (5) when W represents =O, or compound of formula (6) to ring-opening, removal of any P1 protecting groups, and optionally removing any additional protecting groups to give a compound of formula (7). In step (e), any P1 protecting groups and any additional protecting groups may be removed individually or together and prior to ring opening, during ring opening or after ring opening of the compounds of formula (5) or (6). Preferably, in steps (a) to (c), W is OP2 for the compounds of formula (1), (2), (3) and (5). Protecting groups which may be represented by P1 and P2 include alcohol protecting groups, examples of which are well known in the art. Particular examples include tetrahydropyranyl, benzyl and methyl groups, and optionally substituted variants thereof. Substituents may advantageously be used to modify the ease of introduction or removal of the protecting group. Preferred protecting groups are silyl groups, for example triaryl- and especially trialkylsilyl groups. Especially preferred examples are trimethylsilyl, t-butyldimethylsilyl and t-butyldiphenylsilyl groups. Protecting groups which may be represented by P1 and P2 may be the same or different. When the protecting groups P1 and P2 are different, advantageously this may allow for the selective removal of only P1 or P2. Preferably, when the protecting groups P1 and P2 are different, P1 is a tetrahydropyranyl, benzyl, or silyl group and P2 is a methyl group. More preferably, when the protecting groups P1 and P2 are different, P1 is a benzyl, or silyl group and P2 is a methyl group. Protecting groups which may be represented by R3 and R4 include amine protecting groups, examples of which are well known in the art. Particular examples include benzyl groups, carbamates (such as CBZ, Boc, Fmoc), phosphate, thiophosphate, silyl groups and, when R3 and R4 together are a single protecting group, an imine group. Hyrdoxylation of compounds of formula (1) can be achieved by methods known in the art for displacing a halo group with a hydroxide source. Preferably, the process comprises contacting the compound of formula (1) with a source of hydroxide. Hydroxide sources include hydroxide salts, especially ammonium or alkali metal hydroxides, particularly lithium, sodium or potassium hydroxide, and various aqueous media such as water in the presence of basic media such as N-methylpryrrolidinone, HMPA, Al2O3, CaCO3, Na2CO3, K2CO3 or KO2/18-crown-6, silver salts such as AgNO3 or, Ag2O, or oxidants such perbenzioc acid. A particularly preferred process comprises contacting the compound of formula (1) with 5 molar equivalents of KOH in the presence of dimethylsulfoxide solvent at a temperature of, for example, about 50°C. Alternatively, hydroxylation may be achieved by first displacing the halogen with a leaving group such as acetate, triflate or sulphate optionally in the presence of a silver salt, then displacing the leaving group with a hydroxide source. A particularly preferred process comprises contacting the compound of formula (1) with 3 molar equivalents of NaOAc in the presence of dimethylformamide solvent and tetra-n-butylammonium chloride at a temperature of, for example, about 100°C, isolating the acetyl compound and contacting with potassium carbonate in the presence of methanol solvent and at a temperature of, for example, about 0°C. Oxidation of compounds of formula (2) can be achieved using oxidation systems known in the art for the oxidation of alcohols, especially those known in the art for the oxidation of primary alcohols. Examples include oxidation with Dess-Martin periodinane, bromine, Swern oxidation or various metal based oxidations such as Fetizon reagent, manganate based reagents, and chromate based reagents such as Collins reagent. Swern oxidation is preferred. When Swern oxidation is employed, preferred conditions comprise the use of dimethyl sulphoxide and oxalyl chloride or bromine in a solvent such as dichloromethane or dichlormethane/THF mixtures, at reduced temperature, such as , from 0 to -100°C, preferably -50 to -80°C. Preferably, reagents are added at reduced temperature, such as -30 to -80°C, and then once all reagents are added, the reaction mixture is allowed to warm to 15 to 20°C. Alternatively, the compound of formula (3) may be obtained directly from a compound of formula (1), for example by treatment with dimethysulphoxide and an acid acceptor. The coupling of the compound of formula (3) with the compound of formula (4) may employ conditions analogous to those given in WO01/85702 for the corresponding coupling of a compound of formula (4). Alternatively, conditions comprising refluxing the compounds of formula (3) and (4) in a hydrocarbon solvent, such as toluene or cycfohexane, or mixtures thereof, followed by contact with aqueous acid, such as aqueous HCI may be employed. Alkyl, aryl, alkoxy or aryloxy groups which may be represented by R7 and R8 include C^alkyl groups, slich as methyl and ethyl groups, C8-12aryl groups, such phenyl, tolyl or naphthyl, C1-6alkoy groups, such as ethoxy groups, and C6-10aryloxy groups such as phenoxy groups. Anions which may be represented by X include halide. R6 preferably is P(=O)R7R8 where R7 and R8 each independently is an alkyl, aryl, aikoxy or aryloxy group, preferably a phenyl group. When W represents OP2, the protecting group may be removed to form a hydroxy group by methods known in the art for the removal of the given protecting group. For example, silyl protecting groups may be removed by contact with a source of fluoride ion, such as tetrabutylammonium fluoride. Oxidation of compounds formed by deprotection of compounds wherein W represents -OP2 may employ conditions known in the art for the oxidation of pyranols to pyranones, and include those given in "Comprehensive Organic Transformations", R.C. Larock, 2nd Ed (1999) p 1670, published by Wiley VCH, incorporated herein by reference. Preferred oxidation systems include Ag2CO3/Celite, especially Celite J2, bromine or Swern. Ring opening of the compounds of formula (5), when W represent =0 or formula (6) may employ conditions known in the art for ring opening of a pyranone. Preferably, the ring is opened by contact with a base, such as sodium hydroxide or calcium oxide. Conveniently, polar solvents are employed, for example methanol, acetonitrile, tetrahydrofuran or mixtures thereof. Remaining protecting groups may be removed by methods known in the art for the removal of the given protecting group. For example, silyl protecting groups may be removed by contact with a source of fluoride ion, such as tetrabutylammonium fluoride, and benzyl -groups may be removed by treatment with TMSI or under selective hydrogenation conditions. It will also be recognised that compounds of formulae (2), (3) and (5) may also be subjected to oxidation (when W represents -OH) or deprotection and oxidation (when W represents (-O-protecting group) to form the corresponding compound wherein W represents =O. Preferred compounds of formula (1) are compounds of formula: wherein W, P1 and Y are as previously described. Preferred compounds of formula (2) are compounds of formula: wherein W and P1 are as previously described. Preferred compounds of formula (3) are compounds of formula: wherein W and P1 are as previously described. Preferred compounds of formula (5) are of formula: _ _ 4 wherein R1, R2, W and P1 are as previously described. Preferred compounds of formula (6) are of formula: wherein R1 and R2 are as previously described. wherein R1 and R2 are as previously described. Compounds of formula (7) are advantageously converted to pharmaceutically acceptable salts, especially their calcium salts (for example WO01/60804). Compounds of formula (4) are advantageously prepared by the methods given in WO00/49014 and WO01/85702. Particularly preferred compounds of formula (4) are compounds of formula: Compounds of formula (1) are advantageously prepared by enzyme catalysed condensation of acetaldehyde and 2-haloacetaldehyde, for example using the method given in US patent 5,795,749. Compounds of formulae (2) and (3) and, when W is OP2, formula (5) form further aspects of the present invention. The invention is illustrated by the following examples. Example 1 - Preparation of Chlorolactol methyl acetal ((2S,4R)-2-(chloromethyl)-6- methoxytetrahydro-2H-pyran-4-ol), a compound of Formula 1 where Y = CI, P1 = H and W = -OP2, in which P2 = Me. Crude chlorolactol (15g) was dissolved in methanol (150ml) and heated to 40°C for 2 hours in the presence of 0.1ml sulphuric acid. The solvent was removed by rotary evaporation to afford the product as a dark brown flowing oil. The product was dissolved in DCM and washed with sodium bicarbonate solution. The solvent was removed by rotary evaporation to afford the product as a dark brown flowing oil, which was purified by column chromatography (16.1g) containing a mixture of anomers m/z 179, 149 and 113; 1H nmr CDCI3 3.6-3.7 (m 2H), 4.1 (m 1H), 1.5-1.6 (m 2H), 4.0 (m 1H), 1.3-1.6 (m 2H), 4.9 (m 1H), 3.3 & 3.5 (s 3H); 13C nmr CDCI3 32, 36, 45, 55&56, 64, 65, 94. Example 2 - Preparation of O-benzyl-chlorolactol methyl acetal ((2S,4R)-4- (benzyloxy)-2-(chloromethyl)-6-methoxytetrahydro-2H-pyran), a compound of Formula 1 where Y = CI, P1= Bn and W = -OP2, in which P2 = Me. Chlorolactol methyl acetal (1g) was dissolved in THF (5ml) and charged to sodium hydride (0.33g 60% in mineral oil) in THF (5ml) at room temperature. Benzyl bromide (1.9g) was added dropwise and the mass heated to 80°C for 2 hours. Methanol (2ml) was added and the mass was partitioned between DCM/ water, and was then washed with water. The organic phase was dried and the solvent was removed by rotary evaporation to afford an orange flowing oil (2.1g), containing a mixture of anomers containing a mixture of anomers. m/z 270; 238; 203; 132; 91; 1H nmr CDCI31.6-2.0 (m 4H), 3.4 & 3.5 (s 3H), 3.6 (m 2H), 3.8 (m 1H), 4.0 (m 1H), 4.5 (m 2H), 4.7 (m 1H), 7.3-7.5 (m 5H); 13C nmr CDCI3 32&33, 46, 55&56, 58, 66, 74, 96&98,128-131. Example 3 - Preparation of Hydroxy-O-benzyl-lactol methyl acetal ([(2R,4R)-4- (benzyloxy)-6-methoxytetrahydro-2H-pyran-2-yl]methanol), a compound of Formula 2 where P1 = Bn and W = -OP2, in which P2 = Me. Preparation of the Acetate Intermediate: To a 3-litre three necked round bottomed flask flushed with dry nitrogen the O- benzyl-chlorolactol methyl acetal (30g) was charged into dry N-methyt pyrollidinone (756mls). Anhydrous tetrabutylammonium acetate (102.57g) was also charged to the solution. The reaction mixture was then heated at 100°C for 24 hours. The reaction mixture was sampled at routine intervals and directly analysed by tic and gc/ms. The black solution was then diluted with water (150mls) and extracted with ethyl acetate (3 x 1500mls). The combined upper organic layer was then washed with water (3 x 1500mls). The aqueous portion showed no product content at this point. The layers were then separated, dried, (Na2SO4) and the solvent removed in vacuo to yield a black flowing oil (31 g, 95%) containing a mixture of anomers. 1H nmr CDCIs 1.4-1.8 (m 4H), 2.0- 2.1 ( duplicate s, 3H), 3.4 & 3.5 (s 3H), 3.8 (m 1H), 4.0 (m 1H), 4.1 (m 2H), 4.5 (m, 2H), 4.7-4.9 (m 1H), 7.2-7.3 (m, 5H); 13C nmr CDCI3 20.8; 30-35; 55&56; 57&64; 66&68; 69&72; 70&71; 98&99; 127-128 & 138; 170.5; m/z 293, 262,221, 203, 156,91 and 43. Preparation of the Alcohol from the Acetate Intermediate: To a 50mls three necked round bottomed flask flushed with dry nitrogen the O- benzyl-chlorolactol methyl acetal acetate (2g) was charged into dry methanol (10mls) containing anhydrous potassium carbonate (1g). The resultant suspension was stirred at 20°C for 30 minutes. G.C/M.S. showed complete conversion of acetate to alcohol. The solid was filtered off and the solvent removed in vacuo to yield a brown flowing oil containing a mixture of anomers (1.6g, 93%). 1H nmr CDCI3 1.4-1.8 (m 4H), 3.4 & 3.5 (s 3H), 3.8 (m 1H), 3.9 (m 1H), 4.0 (m 2H), 4.5 (m 2H), 4.7-4.9 (m 1H), 7.2-7.3 (m, 5H); 1SC nmr CDCI3 30-38; 55&56; 65&66; 65&69; 70&71; 72&73; 99&100; 128 & 140; m/z 252, 221,189,163,114 and 91. Example 4 - Preparation of formyl-O-benzyl-lactol methyl acetal (2S,4R)-4- (benzyloxy)-6-methoxytetrahydro-2H-pyran-2-carbaldehyde a compound of Formula 3 where P1 = Bn and W = -OP2, in which P2 = Me. Dess-Martin periodinane reagent (1.91g) in dichloromethane (50mls) was charged to a 1000 mis round bottomed flask purged with dry nitrogen. The hydroxy-O-benzyl-lactol methyl acetal (1.0g,) was dissolved in dichloromethane (50mls) and added to the Dess- Martin periodinane reagent at 20°C. The reaction mixture was then stirred at room temperature for 30 minutes. The reaction was monitored by tic. The reaction mixture was then diluted with diethyl ether (500 mis) to precipitate the excess reagent. The suspension was then washed with 10% aqueous sodium hydroxide (200mls). The upper organic layer was then washed with water (250mls). The upper organic layer was then separated, dried (Na2SO4) and the solvent removed in vacuo to yield a dark flowing oH as a mixture of anomers (0.8g). 1H nmr CDCI3 1.6-1.9 (m 4H), 3.3 & 3.5 (s 3H), 3.7 (m 1H), 3.8 (m 1H), 4.4 (m 2H), 4.7-4.9 (m 1H), 7.2-8.1 (m, 5H), 9.6-9.7 (2 x s, 1H). 13C nmr CDCI3 30-38; 55&56; 65&66; 65&69; 70&71; 99&100; 128 & 140; 201. m/z250,221,189,163,143,117 and 91. Alternatively, a Swern oxidation can be carried out as illustrated by the following example: A stirred solution of oxalyl chloride (0.037 cm3, 0.44 mmol) in dichloromethane (4 cm3) under nitrogen was cooled to -78 C and DMSO was added in one portion. A solution of the alcohol (100 mg, 0.40 mmol) in dichloromethane (1 cm3) was added to the reaction mixture and the reaction mixture stirred at -78 C for 5 min. Triethylamine (0.272 cm3, 19.8 mmol) was added and the resulting solution was stirred at -78 C for 25 min and used immediately without isolation or purification. Tic rf 0.40 ethyl acetate:hexane (1:1) orange spot with 2,4-dinitrophenylhydrazine stain Example 5 - Preparation of Pyrimidyl-ethenyl-O-benzyl-lactol methyl acetal, a compound of Formula 5 where R1= IPr, R2= 4-FCeH4, R3=Me, R4=SOzMe, P1 = Bz and W = -OP2, in which P2 = Me. Pyrimidyl-ethenyl-O-benzyl-lactol methyl acetal was obtained by first dissolving 0.21g of the compound of formula 4 wherein R3=Me, R4=SO2Me and R8=PO(Ph)2 in 10ml dry THF, cooling to -60°C and then adding 0.2ml of a 2M solution of sodium hexamethyldisilazide. After 20min, a solution of 0.1g formyl-O-benzyl-lactol methyl acetal in 10ml dry THF at -30°C was added. The reaction mixture was then maintained at this temperature for 8 hours and monitored by tic. The reaction mixture was allowed to slowly warm up to 20°C. Glacial acetic (5mls) acid was then charged to quench the reaction. Water (5mls) was also charged to the mixture. The solvent was then removed in vacuo and reconstituted with toluene (15mls) and water (15mls). The upper organic layer was then separated and the aqueous layer was then washed with ethyl acetate (15 mis). The combined organics were then dried and the solvent removed in vacuo to yield an oil containing a mixture of isomers, that can be purified by chromatography. The desired product had the tentative NMR assignment 1H nmr CDCI3 1.2 (d, 6H), 1.6-1.9 (m 4H), 3.3 (s, 3H), 3.4 (s, 3H), 3.2 & 3.5 (2 x s, 3H), 3.7 (m 1H), 3.8 (m 1H). 4.2 (m 1H), 4.4 (m 2H), 4.7-4.9 (m 1H), 5.35 (dd, 1H), 5.85-6.7 (d, 1H), 7.1-8.1 (m,9H). Example 6 - Preparation of Pyrimidyl-ethenyl-OH-lactol methyl acetal (Rosuvastatin Lactol-OMe) a compound of Formula 5 where R1= IPr, R2= 4-FC6H4, R3=Me, R4=SO2Me, P1 = H and W =-OP2, in which P2 = Me. Pyrimidyl-ethenyl-OH-lactol methyl acetal may be obtained by reaction of Pyrimidyl-ethenyl-O-benzyl-lactol methyl acetal with TMSI. Example 7 • Preparation of Pyrimidyl-ethenyl-OH-lactol (Rosuvastatin Lactol), a compound of Formula 5 where R1= IPr, R2= 4-FC6H4, R3=Me, R4=SO2Me, P1 = H and W = -OP2,in which P2 = H Pyrimidyl-ethenyl-OH-lactol may be obtained by treatment of the Pyrimidyl-ethenyl- OH-lactol methyl acetal with 0.1N HCI in methanol. Example 8 - Preparation of Lactone, a compound of Formula 6 where R1= iPr, R2= 4-FC8H4, R3=Me, R4=SO2Me, P1=H The pyrimidyl-ethenyl-OH-lactol (35mg, 0.065mmol) in dichloromethane (0.5ml) was added to Dess-Martin periodinane (30mg, 0,07mmol) and stirred at room temperature for 2.5 hours. The reaction was partitioned between 1M sodium hydroxide and diethyl ether. The phases were then separated and the organic volume reduced in vaccuo to afford the crude product oil. Example 9 - Preparation of Rosuvastatin (hydrolysis of Lactone), a coumpound of Formula 7 where R1= iPr, R2= 4-FC6H4, R3=Me, R4=SO2Me The lactone (1.1g) was dissolved in ethanol (10ml). Water (2ml) and Ca(OH)2 (0.15g) were added and the suspension warmed to 60°C for 3 hours. A further 10ml of warm water was added, then the mixture allowed to cool slowly to room temperature. The precipitate formed was filtered and dried to give Rosuvastatin calcium salt. The material was identical to an authentic sample by mixed melting point, NMR and mass spectrometry. We claim, 1. A process for the preparation of a compound of formula (7): wherein R1 represents an alkyl group, such as a C1-6 alkyl group, and preferably an isopropyl group; R2 represents an aryl group, preferably a 4-iluorophenyl group; R3 represents hydrogen, a protecting group or an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; and R4 represents hydrogen, a protecting group or a SO2R5 group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group, which comprises a) hydroxylating a compound of formula (1): wherein Y represents a halo group, preferably Cl or Br; P1 represents hydrogen or a protecting group, and W represents -OP2, in which P2 represents hydrogen or a protecting group, to give a compound of formula (2): b) oxidising the compound of formula (2) to give a compound of formula (3): c) coupling the compound of formula (3) with a compound of formula (4): i wherein R3 represents a protecting group or an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; and R6 represents (PR7R8 )+X- or P(=O)R7R8 in which X is an anion and R7 and R8 each independently is an alkyl. aryl. alkoxy or aryloxy group, preferably a phenyl group. to give a compound of formula (5): wherein R3 represents a protecting group or an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; and R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group, d) removing any P2 protecting group and oxidising the compound of formula (5) to give a compound of formula (6): and e) subjecting the compound of formula (6) to ring-opening, removal of any P1 protecting groups, and optionally removing any additional protecting groups to give a compound of formula (7). 2. A process for preparation of compound of formula 2 as intermediate in the preparation of compound of formula (7), said process includes the step of hydroxylating a compound of formula (1): wherein Y represents a halo group, preferably Cl or Br; P1 represents hydrogen or a protecting group, and W represents -OP2, in which P2 represents hydrogen or a protecting group, to give a compound of formula (2): 3. A process for preparation of compound of formula 3 as intermediate in the preparation of compound of formula (7), said process includes the step of oxidation of compound of formula (2) wherein P1 represents hydrogen or a protecting group, and W represents -OP2, in which P2 represents hydrogen or a protecting group to give a compound of formula (3): 4. A process for the preparation of a compound of formula (5): which comprises coupling the compound of formula (3): with a compound of formula (4): wherein R1 represents an alkyl group, such as a C1-6 alkyl group, and preferably an isopropyl group; R2 represents an aryl group, preferably a 4-fluorophenyl group; R3 represents a protecting group or an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; and R6 represents (PR7R8)+X- or P(=O)R7R8 in which X is an anion and R7 and R8 each independently is an alkyl, aryl, alkoxy or aryloxy group, preferably a phenyl group, P2 represents hydrogen or a protecting group; and W represents -OP2, in which P2 represents hydrogen or a protecting group. 5. A compound of formula (5): wherein R1 represents an alkyl group, such as a C1-6 alkyl group, and preferably an isopropyl group; R2 represents an aryl group, preferably a 4-fiuorophenyl group; R3 represents hydrogen, a protecting group or an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably a methyl group; P1 represents hydrogen or a protecting group; and W represents -OP2, in which P2 represents hydrogen or a protecting group. There is provided a process for the preparation of a compound of formula (7) wherein R1 represents an alkyl group; R2 represents an aryl group; R3 represents hydrogen, a protecting group or an alkyl group; and R4 represents hydrogen, a protecting group or a SO2R5 group where R5 is an alkyl group, which comprises a) hydroxylating a compound of formula (1) wherein Y represents a halo group; P1 represents hydrogen or a protecting group, and W represents =O or -OP2, in which P2 represents hydrogen or a protecting group, to give a compound of formula (2), b) oxidising the compound of formula (2) to give a compound of formula (3), c) coupling the compound of formula (3) with a compound of formula (4), wherein R3 represents a protecting group or an alkyl group; R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group; and R6 represents (PR7R8)+X- or P(=O)R7R8 in which X is an anion and R7 and R8 each independently is an alkyl, aryl.

Full Text

The present invention concerns a process and intermediate compounds useful in
the preparation of statins, particularly Rosuvastatin.
According to the present invention, there is provided a process for the preparation
of a compound of formula (7):

wherein
R1 represents an alkyl group, such as a C1-6 alkyl group, and preferably an
isopropyl group;
R2 represents an aryl group, preferably a 4-fluorophenyl group;
R3 represents hydrogen, a protecting group or an alkyl group, such as a C1-6 alkyl
group, and preferably a methyl group; and
R4 represents hydrogen, a protecting group or a SO2R5 group where R5 is an alkyl
group, such as a C1-6 alkyl group, and preferably a methyl group,
which comprises
a) hydroxylating a compound of formula (1):

wherein Y represents a halo group, preferably CI or Br; P1 represents hydrogen or
a protecting group, and W represents =O or -OP2, in which P2 represents
hydrogen or a protecting group,
to give a compound of formula (2):

b) oxidising the compound of formula (2) to give a compound of formula (3):
1
c) coupling the compound of formula (3) with a compound of formula (4):

wherein R3 represents a protecting group or an alkyl group, such as a C1-6 alkyl
group, and preferably a methyl group; R4 represents a protecting group or a SO2R5
group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably a
methyl group; and R6 represents (PR7R8)+X- or P(=O)R7R8 In which X is an anion
and R7 and R8 each independently is an alkyl, aryl, alkoxy or aryloxy group,
preferably a phenyl group,
to give a compound of formula (5):

wherein R3 represents a protecting group or an alkyl group, such as a C1-5 alkyl
group, and preferably a methyl group; and R4 represents a protecting group or a
SO2R5 group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably
a methyl group,
d) when W represents -OP2, removing any P2 protecting group and oxidising, the
compound of formula (5) to give a compound of formula (6):

and
e) subjecting the compound of formula (5) when W represents =O, or compound of
formula (6) to ring-opening, removal of any P1 protecting groups, and optionally removing
any additional protecting groups to give a compound of formula (7).
In step (e), any P1 protecting groups and any additional protecting groups may be
removed individually or together and prior to ring opening, during ring opening or after ring
opening of the compounds of formula (5) or (6).
Preferably, in steps (a) to (c), W is OP2 for the compounds of formula (1), (2), (3)
and (5).
Protecting groups which may be represented by P1 and P2 include alcohol
protecting groups, examples of which are well known in the art. Particular examples

include tetrahydropyranyl, benzyl and methyl groups, and optionally substituted variants
thereof. Substituents may advantageously be used to modify the ease of introduction or
removal of the protecting group. Preferred protecting groups are silyl groups, for example
triaryl- and especially trialkylsilyl groups. Especially preferred examples are trimethylsilyl,
t-butyldimethylsilyl and t-butyldiphenylsilyl groups.
Protecting groups which may be represented by P1 and P2 may be the same or
different. When the protecting groups P1 and P2 are different, advantageously this may
allow for the selective removal of only P1 or P2. Preferably, when the protecting groups P1
and P2 are different, P1 is a tetrahydropyranyl, benzyl, or silyl group and P2 is a methyl
group. More preferably, when the protecting groups P1 and P2 are different, P1 is a
benzyl, or silyl group and P2 is a methyl group.
Protecting groups which may be represented by R3 and R4 include amine
protecting groups, examples of which are well known in the art. Particular examples
include benzyl groups, carbamates (such as CBZ, Boc, Fmoc), phosphate, thiophosphate,
silyl groups and, when R3 and R4 together are a single protecting group, an imine group.
Hyrdoxylation of compounds of formula (1) can be achieved by methods known in
the art for displacing a halo group with a hydroxide source. Preferably, the process
comprises contacting the compound of formula (1) with a source of hydroxide. Hydroxide
sources include hydroxide salts, especially ammonium or alkali metal hydroxides,
particularly lithium, sodium or potassium hydroxide, and various aqueous media such as
water in the presence of basic media such as N-methylpryrrolidinone, HMPA, Al2O3,
CaCO3, Na2CO3, K2CO3 or KO2/18-crown-6, silver salts such as AgNO3 or, Ag2O, or
oxidants such perbenzioc acid. A particularly preferred process comprises contacting the
compound of formula (1) with 5 molar equivalents of KOH in the presence of
dimethylsulfoxide solvent at a temperature of, for example, about 50°C.
Alternatively, hydroxylation may be achieved by first displacing the halogen with a
leaving group such as acetate, triflate or sulphate optionally in the presence of a silver
salt, then displacing the leaving group with a hydroxide source. A particularly preferred
process comprises contacting the compound of formula (1) with 3 molar equivalents of
NaOAc in the presence of dimethylformamide solvent and tetra-n-butylammonium chloride
at a temperature of, for example, about 100°C, isolating the acetyl compound and
contacting with potassium carbonate in the presence of methanol solvent and at a
temperature of, for example, about 0°C.
Oxidation of compounds of formula (2) can be achieved using oxidation systems
known in the art for the oxidation of alcohols, especially those known in the art for the
oxidation of primary alcohols. Examples include oxidation with Dess-Martin periodinane,
bromine, Swern oxidation or various metal based oxidations such as Fetizon reagent,
manganate based reagents, and chromate based reagents such as Collins reagent.
Swern oxidation is preferred. When Swern oxidation is employed, preferred conditions

comprise the use of dimethyl sulphoxide and oxalyl chloride or bromine in a solvent such
as dichloromethane or dichlormethane/THF mixtures, at reduced temperature, such as
, from 0 to -100°C, preferably -50 to -80°C. Preferably, reagents are added at reduced
temperature, such as -30 to -80°C, and then once all reagents are added, the reaction
mixture is allowed to warm to 15 to 20°C.
Alternatively, the compound of formula (3) may be obtained directly from a
compound of formula (1), for example by treatment with dimethysulphoxide and an acid
acceptor.
The coupling of the compound of formula (3) with the compound of formula (4)
may employ conditions analogous to those given in WO01/85702 for the corresponding
coupling of a compound of formula (4). Alternatively, conditions comprising refluxing the
compounds of formula (3) and (4) in a hydrocarbon solvent, such as toluene or
cycfohexane, or mixtures thereof, followed by contact with aqueous acid, such as aqueous
HCI may be employed.
Alkyl, aryl, alkoxy or aryloxy groups which may be represented by R7 and R8
include C^alkyl groups, slich as methyl and ethyl groups, C8-12aryl groups, such phenyl,
tolyl or naphthyl, C1-6alkoy groups, such as ethoxy groups, and C6-10aryloxy groups such
as phenoxy groups.
Anions which may be represented by X include halide.
R6 preferably is P(=O)R7R8 where R7 and R8 each independently is an alkyl, aryl,
aikoxy or aryloxy group, preferably a phenyl group.
When W represents OP2, the protecting group may be removed to form a hydroxy
group by methods known in the art for the removal of the given protecting group. For
example, silyl protecting groups may be removed by contact with a source of fluoride ion,
such as tetrabutylammonium fluoride.
Oxidation of compounds formed by deprotection of compounds wherein W
represents -OP2 may employ conditions known in the art for the oxidation of pyranols to
pyranones, and include those given in "Comprehensive Organic Transformations", R.C.
Larock, 2nd Ed (1999) p 1670, published by Wiley VCH, incorporated herein by reference.
Preferred oxidation systems include Ag2CO3/Celite, especially Celite J2, bromine or
Swern.
Ring opening of the compounds of formula (5), when W represent =0 or formula
(6) may employ conditions known in the art for ring opening of a pyranone. Preferably,
the ring is opened by contact with a base, such as sodium hydroxide or calcium oxide.
Conveniently, polar solvents are employed, for example methanol, acetonitrile,
tetrahydrofuran or mixtures thereof.
Remaining protecting groups may be removed by methods known in the art for the
removal of the given protecting group. For example, silyl protecting groups may be
removed by contact with a source of fluoride ion, such as tetrabutylammonium fluoride,

and benzyl -groups may be removed by treatment with TMSI or under selective
hydrogenation conditions.
It will also be recognised that compounds of formulae (2), (3) and (5) may also be
subjected to oxidation (when W represents -OH) or deprotection and oxidation (when W
represents (-O-protecting group) to form the corresponding compound wherein W
represents =O.
Preferred compounds of formula (1) are compounds of formula:

wherein W, P1 and Y are as previously described.
Preferred compounds of formula (2) are compounds of formula:

wherein W and P1 are as previously described.
Preferred compounds of formula (3) are compounds of formula:

wherein W and P1 are as previously described.
Preferred compounds of formula (5) are of formula:
_ _ 4
wherein R1, R2, W and P1 are as previously described.
Preferred compounds of formula (6) are of formula:

wherein R1 and R2 are as previously described.

wherein R1 and R2 are as previously described.
Compounds of formula (7) are advantageously converted to pharmaceutically
acceptable salts, especially their calcium salts (for example WO01/60804).
Compounds of formula (4) are advantageously prepared by the methods given in
WO00/49014 and WO01/85702. Particularly preferred compounds of formula (4) are
compounds of formula:

Compounds of formula (1) are advantageously prepared by enzyme catalysed
condensation of acetaldehyde and 2-haloacetaldehyde, for example using the method
given in US patent 5,795,749.
Compounds of formulae (2) and (3) and, when W is OP2, formula (5) form further
aspects of the present invention.
The invention is illustrated by the following examples.
Example 1 - Preparation of Chlorolactol methyl acetal ((2S,4R)-2-(chloromethyl)-6-
methoxytetrahydro-2H-pyran-4-ol), a compound of Formula 1 where Y = CI, P1 = H
and W = -OP2, in which P2 = Me.
Crude chlorolactol (15g) was dissolved in methanol (150ml) and heated to 40°C for
2 hours in the presence of 0.1ml sulphuric acid. The solvent was removed by rotary
evaporation to afford the product as a dark brown flowing oil. The product was dissolved
in DCM and washed with sodium bicarbonate solution. The solvent was removed by
rotary evaporation to afford the product as a dark brown flowing oil, which was purified by
column chromatography (16.1g) containing a mixture of anomers m/z 179, 149 and 113;
1H nmr CDCI3 3.6-3.7 (m 2H), 4.1 (m 1H), 1.5-1.6 (m 2H), 4.0 (m 1H), 1.3-1.6 (m 2H), 4.9
(m 1H), 3.3 & 3.5 (s 3H); 13C nmr CDCI3 32, 36, 45, 55&56, 64, 65, 94.

Example 2 - Preparation of O-benzyl-chlorolactol methyl acetal ((2S,4R)-4-
(benzyloxy)-2-(chloromethyl)-6-methoxytetrahydro-2H-pyran), a compound of
Formula 1 where Y = CI, P1= Bn and W = -OP2, in which P2 = Me.
Chlorolactol methyl acetal (1g) was dissolved in THF (5ml) and charged to sodium
hydride (0.33g 60% in mineral oil) in THF (5ml) at room temperature. Benzyl bromide
(1.9g) was added dropwise and the mass heated to 80°C for 2 hours. Methanol (2ml) was
added and the mass was partitioned between DCM/ water, and was then washed with
water. The organic phase was dried and the solvent was removed by rotary evaporation
to afford an orange flowing oil (2.1g), containing a mixture of anomers containing a
mixture of anomers. m/z 270; 238; 203; 132; 91; 1H nmr CDCI31.6-2.0 (m 4H), 3.4 & 3.5
(s 3H), 3.6 (m 2H), 3.8 (m 1H), 4.0 (m 1H), 4.5 (m 2H), 4.7 (m 1H), 7.3-7.5 (m 5H); 13C
nmr CDCI3 32&33, 46, 55&56, 58, 66, 74, 96&98,128-131.
Example 3 - Preparation of Hydroxy-O-benzyl-lactol methyl acetal ([(2R,4R)-4-
(benzyloxy)-6-methoxytetrahydro-2H-pyran-2-yl]methanol), a compound of Formula
2 where P1 = Bn and W = -OP2, in which P2 = Me.
Preparation of the Acetate Intermediate:
To a 3-litre three necked round bottomed flask flushed with dry nitrogen the O-
benzyl-chlorolactol methyl acetal (30g) was charged into dry N-methyt pyrollidinone
(756mls). Anhydrous tetrabutylammonium acetate (102.57g) was also charged to the
solution. The reaction mixture was then heated at 100°C for 24 hours. The reaction
mixture was sampled at routine intervals and directly analysed by tic and gc/ms.
The black solution was then diluted with water (150mls) and extracted with ethyl
acetate (3 x 1500mls). The combined upper organic layer was then washed with water (3
x 1500mls). The aqueous portion showed no product content at this point. The layers
were then separated, dried, (Na2SO4) and the solvent removed in vacuo to yield a black
flowing oil (31 g, 95%) containing a mixture of anomers. 1H nmr CDCIs 1.4-1.8 (m 4H), 2.0-
2.1 ( duplicate s, 3H), 3.4 & 3.5 (s 3H), 3.8 (m 1H), 4.0 (m 1H), 4.1 (m 2H), 4.5 (m, 2H),
4.7-4.9 (m 1H), 7.2-7.3 (m, 5H); 13C nmr CDCI3 20.8; 30-35; 55&56; 57&64; 66&68;
69&72; 70&71; 98&99; 127-128 & 138; 170.5; m/z 293, 262,221, 203, 156,91 and 43.
Preparation of the Alcohol from the Acetate Intermediate:
To a 50mls three necked round bottomed flask flushed with dry nitrogen the O-
benzyl-chlorolactol methyl acetal acetate (2g) was charged into dry methanol (10mls)
containing anhydrous potassium carbonate (1g). The resultant suspension was stirred at
20°C for 30 minutes. G.C/M.S. showed complete conversion of acetate to alcohol. The
solid was filtered off and the solvent removed in vacuo to yield a brown flowing oil
containing a mixture of anomers (1.6g, 93%). 1H nmr CDCI3 1.4-1.8 (m 4H), 3.4 & 3.5 (s

3H), 3.8 (m 1H), 3.9 (m 1H), 4.0 (m 2H), 4.5 (m 2H), 4.7-4.9 (m 1H), 7.2-7.3 (m, 5H); 1SC
nmr CDCI3 30-38; 55&56; 65&66; 65&69; 70&71; 72&73; 99&100; 128 & 140; m/z 252,
221,189,163,114 and 91.
Example 4 - Preparation of formyl-O-benzyl-lactol methyl acetal (2S,4R)-4-
(benzyloxy)-6-methoxytetrahydro-2H-pyran-2-carbaldehyde a compound of Formula
3 where P1 = Bn and W = -OP2, in which P2 = Me.
Dess-Martin periodinane reagent (1.91g) in dichloromethane (50mls) was charged to a
1000 mis round bottomed flask purged with dry nitrogen. The hydroxy-O-benzyl-lactol
methyl acetal (1.0g,) was dissolved in dichloromethane (50mls) and added to the Dess-
Martin periodinane reagent at 20°C. The reaction mixture was then stirred at room
temperature for 30 minutes. The reaction was monitored by tic. The reaction mixture was
then diluted with diethyl ether (500 mis) to precipitate the excess reagent. The suspension
was then washed with 10% aqueous sodium hydroxide (200mls). The upper organic layer
was then washed with water (250mls). The upper organic layer was then separated, dried
(Na2SO4) and the solvent removed in vacuo to yield a dark flowing oH as a mixture of
anomers (0.8g).
1H nmr CDCI3 1.6-1.9 (m 4H), 3.3 & 3.5 (s 3H), 3.7 (m 1H), 3.8 (m 1H), 4.4 (m 2H), 4.7-4.9
(m 1H), 7.2-8.1 (m, 5H), 9.6-9.7 (2 x s, 1H).
13C nmr CDCI3 30-38; 55&56; 65&66; 65&69; 70&71; 99&100; 128 & 140; 201.
m/z250,221,189,163,143,117 and 91.
Alternatively, a Swern oxidation can be carried out as illustrated by the following example:
A stirred solution of oxalyl chloride (0.037 cm3, 0.44 mmol) in dichloromethane (4 cm3)
under nitrogen was cooled to -78 C and DMSO was added in one portion. A solution of
the alcohol (100 mg, 0.40 mmol) in dichloromethane (1 cm3) was added to the reaction
mixture and the reaction mixture stirred at -78 C for 5 min. Triethylamine (0.272 cm3,
19.8 mmol) was added and the resulting solution was stirred at -78 C for 25 min and
used immediately without isolation or purification. Tic rf 0.40 ethyl acetate:hexane (1:1)
orange spot with 2,4-dinitrophenylhydrazine stain
Example 5 - Preparation of Pyrimidyl-ethenyl-O-benzyl-lactol methyl acetal, a
compound of Formula 5 where R1= IPr, R2= 4-FCeH4, R3=Me, R4=SOzMe, P1 = Bz and
W = -OP2, in which P2 = Me.

Pyrimidyl-ethenyl-O-benzyl-lactol methyl acetal was obtained by first dissolving
0.21g of the compound of formula 4 wherein R3=Me, R4=SO2Me and R8=PO(Ph)2 in 10ml
dry THF, cooling to -60°C and then adding 0.2ml of a 2M solution of sodium
hexamethyldisilazide. After 20min, a solution of 0.1g formyl-O-benzyl-lactol methyl acetal
in 10ml dry THF at -30°C was added. The reaction mixture was then maintained at this
temperature for 8 hours and monitored by tic. The reaction mixture was allowed to slowly
warm up to 20°C. Glacial acetic (5mls) acid was then charged to quench the reaction.
Water (5mls) was also charged to the mixture. The solvent was then removed in vacuo
and reconstituted with toluene (15mls) and water (15mls). The upper organic layer was
then separated and the aqueous layer was then washed with ethyl acetate (15 mis). The
combined organics were then dried and the solvent removed in vacuo to yield an oil
containing a mixture of isomers, that can be purified by chromatography. The desired
product had the tentative NMR assignment
1H nmr CDCI3 1.2 (d, 6H), 1.6-1.9 (m 4H), 3.3 (s, 3H), 3.4 (s, 3H), 3.2 & 3.5 (2 x s, 3H),
3.7 (m 1H), 3.8 (m 1H). 4.2 (m 1H), 4.4 (m 2H), 4.7-4.9 (m 1H), 5.35 (dd, 1H), 5.85-6.7 (d,
1H), 7.1-8.1 (m,9H).
Example 6 - Preparation of Pyrimidyl-ethenyl-OH-lactol methyl acetal (Rosuvastatin
Lactol-OMe) a compound of Formula 5 where R1= IPr, R2= 4-FC6H4, R3=Me,
R4=SO2Me, P1 = H and W =-OP2, in which P2 = Me.
Pyrimidyl-ethenyl-OH-lactol methyl acetal may be obtained by reaction of
Pyrimidyl-ethenyl-O-benzyl-lactol methyl acetal with TMSI.
Example 7 • Preparation of Pyrimidyl-ethenyl-OH-lactol (Rosuvastatin Lactol), a
compound of Formula 5 where R1= IPr, R2= 4-FC6H4, R3=Me, R4=SO2Me, P1 = H and
W = -OP2,in which P2 = H
Pyrimidyl-ethenyl-OH-lactol may be obtained by treatment of the Pyrimidyl-ethenyl-
OH-lactol methyl acetal with 0.1N HCI in methanol.
Example 8 - Preparation of Lactone, a compound of Formula 6 where R1= iPr, R2=
4-FC8H4, R3=Me, R4=SO2Me, P1=H
The pyrimidyl-ethenyl-OH-lactol (35mg, 0.065mmol) in dichloromethane (0.5ml)
was added to Dess-Martin periodinane (30mg, 0,07mmol) and stirred at room temperature
for 2.5 hours. The reaction was partitioned between 1M sodium hydroxide and diethyl
ether. The phases were then separated and the organic volume reduced in vaccuo to
afford the crude product oil.

Example 9 - Preparation of Rosuvastatin (hydrolysis of Lactone), a coumpound of
Formula 7 where R1= iPr, R2= 4-FC6H4, R3=Me, R4=SO2Me
The lactone (1.1g) was dissolved in ethanol (10ml). Water (2ml) and Ca(OH)2
(0.15g) were added and the suspension warmed to 60°C for 3 hours. A further 10ml of
warm water was added, then the mixture allowed to cool slowly to room temperature. The
precipitate formed was filtered and dried to give Rosuvastatin calcium salt. The material
was identical to an authentic sample by mixed melting point, NMR and mass
spectrometry.

We claim,
1. A process for the preparation of a compound of formula (7):

wherein
R1 represents an alkyl group, such as a C1-6 alkyl group, and preferably an
isopropyl group;
R2 represents an aryl group, preferably a 4-iluorophenyl group;
R3 represents hydrogen, a protecting group or an alkyl group, such as a C1-6 alkyl
group, and preferably a methyl group; and
R4 represents hydrogen, a protecting group or a SO2R5 group where R5 is an alkyl
group, such as a C1-6 alkyl group, and preferably a methyl group,
which comprises
a) hydroxylating a compound of formula (1):

wherein Y represents a halo group, preferably Cl or Br; P1 represents hydrogen or
a protecting group, and W represents -OP2, in which P2 represents hydrogen or a
protecting group,
to give a compound of formula (2):

b) oxidising the compound of formula (2) to give a compound of formula (3):

c) coupling the compound of formula (3) with a compound of formula (4):

i
wherein R3 represents a protecting group or an alkyl group, such as a C1-6 alkyl
group, and preferably a methyl group; R4 represents a protecting group or a SO2R5
group where R5 is an alkyl group, such as a C1-6 alkyl group, and preferably a
methyl group; and R6 represents (PR7R8 )+X- or P(=O)R7R8 in which X is an anion
and R7 and R8 each independently is an alkyl. aryl. alkoxy or aryloxy group,
preferably a phenyl group.
to give a compound of formula (5):

wherein R3 represents a protecting group or an alkyl group, such as a C1-6 alkyl
group, and preferably a methyl group; and R4 represents a protecting group or a
SO2R5 group where R5 is an alkyl group, such as a C1-6 alkyl group, and
preferably a methyl group,
d) removing any P2 protecting group and oxidising the compound of formula (5) to give a
compound of formula (6):

and
e) subjecting the compound of formula (6) to ring-opening, removal of any P1 protecting
groups, and optionally removing any additional protecting groups to give a compound of
formula (7).
2. A process for preparation of compound of formula 2 as intermediate in the
preparation of compound of formula (7),
said process includes the step of hydroxylating a compound of formula (1):

wherein Y represents a halo group, preferably Cl or Br; P1 represents hydrogen or
a protecting group, and W represents -OP2, in which P2 represents hydrogen or a
protecting group,
to give a compound of formula (2):

3. A process for preparation of compound of formula 3 as intermediate in the
preparation of compound of formula (7),

said process includes the step of oxidation of compound of formula (2)

wherein P1 represents hydrogen or a protecting group, and W represents -OP2, in which
P2 represents hydrogen or a protecting group
to give a compound of formula (3):

4. A process for the preparation of a compound of formula (5):

which comprises coupling the compound of formula (3):

with a compound of formula (4):

wherein
R1 represents an alkyl group, such as a C1-6 alkyl group, and preferably an
isopropyl group;
R2 represents an aryl group, preferably a 4-fluorophenyl group;
R3 represents a protecting group or an alkyl group, such as a C1-6 alkyl group, and
preferably a methyl group;
R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group,
such as a C1-6 alkyl group, and preferably a methyl group; and
R6 represents (PR7R8)+X- or P(=O)R7R8 in which X is an anion and R7 and R8
each independently is an alkyl, aryl, alkoxy or aryloxy group, preferably a phenyl
group,
P2 represents hydrogen or a protecting group; and
W represents -OP2, in which P2 represents hydrogen or a protecting group.
5. A compound of formula (5):

wherein
R1 represents an alkyl group, such as a C1-6 alkyl group, and preferably an
isopropyl group;

R2 represents an aryl group, preferably a 4-fiuorophenyl group;
R3 represents hydrogen, a protecting group or an alkyl group, such as a C1-6 alkyl
group, and preferably a methyl group;
R4 represents a protecting group or a SO2R5 group where R5 is an alkyl group,
such as a C1-6 alkyl group, and preferably a methyl group;
P1 represents hydrogen or a protecting group; and
W represents -OP2, in which P2 represents hydrogen or a protecting group.

There is provided a process for the preparation of a compound of formula (7) wherein R1
represents an alkyl group; R2 represents an aryl group; R3 represents hydrogen, a protecting
group or an alkyl group; and R4 represents hydrogen, a protecting group or a SO2R5 group
where R5 is an alkyl group, which comprises a) hydroxylating a compound of formula (1)
wherein Y represents a halo group; P1 represents hydrogen or a protecting group, and W
represents =O or -OP2, in which P2 represents hydrogen or a protecting group, to give a
compound of formula (2), b) oxidising the compound of formula (2) to give a compound of
formula (3), c) coupling the compound of formula (3) with a compound of formula (4),
wherein R3 represents a protecting group or an alkyl group; R4 represents a protecting group
or a SO2R5 group where R5 is an alkyl group; and R6 represents (PR7R8)+X- or P(=O)R7R8 in
which X is an anion and R7 and R8 each independently is an alkyl, aryl.

PROCESS AND INTERMEDIATE COMPOUNDS USEFUL IN THE PREPARATION OF STATINS, PARTICULARLY ROSUVASTATIN

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