Selective enzymatic esterification and solvolysis of epimeric vitamin D analog and separation of the epimers

A method of selectively enzymatically esterifying the C-24 hydroxyl group of one epimer in a mixture of epimers of a vitamin D analog having a hydroxyl group at the stereogenic C-24 position thereof, comprising the steps of:

• a) providing a solution of mixed C-24 epimers of a vitamin D analog having a hydroxyl group at the C-24 position thereof and an esterifying agent selected from acetyl chloride, acetic anhydride, vinyl acetate and vinyl butyrate in an organic solvent selected from hexane, ethyl acetate, and diisopropyl ether, and
• b) contacting the solution with a lipase selected from Alcaligenes sp. lipase and Psudomonas sp lipase,
• wherein the mixed C-24 epimers are mixtures of C-24 epimers of compounds selected from compounds of general formula III or IX
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• where R1 and R2 are hydrogen or tert-butyldimethylsilyl and R3 is a cyclopropyl or isopropyl group.

A method of enzymatically esterifying the C-24 hydroxyl group of a vitamin D analog having a hydroxyl group at the C-24 position thereof and selected from compounds of general formula III or IX

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• wherein R1 and R2 may be the same or different and represent hydrogen, or hydroxy protecting group, and R3 is a lower alkyl, cycloalkyl, or aryl group comprising the steps of:
• a) providing a solution of the vitamin D analog having a hydroxyl group at the C-24 position thereof and an esterifying agent selected from the group consisting of the acyl halides, the acid anhydrides, and the vinyl esters of lower alkyl carboxylic acids having 2 to 6 carbon atoms in an organic solvent that is a linear or branched alkane having up to 12 carbons, an alkyl ester of an alkyl carboxylic acid, or a dialkyl ether, and
• b) contacting the solution with a lipase selected from Alcaligenes sp. lipase and Psudomonas sp lipase.

A method of selectively enzymatically solvolyzing the esterified C-24 hydroxyl group of one epimer in a mixture of esterified C-24 epimers of a vitamin D analog having an esterified hydroxyl group at the C-24 stereogenic position thereof comprising the steps of:

• a) providing a solution of the mixed esterified C-24 epimers of a vitamin D analog having a hydroxyl group at C-24 and a solvolysis agent that is water or an alkyl alcohol in an organic solvent selected from hexane, diisopropyl ether, and ethyl acetate;
• and
• b) contacting the solution with a lipase selected from Alcaligenes sp. lipase and Pseudomonas sp. lipase;
• wherein
• the mixed esterified C-24 epimers are esters of mixed epimers of compounds of formula general formula III or IX,
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• where R1 and R2 may be the same or different and represent hydrogen or tert-butylsilyl, and R3 is cyclopropyl or iso-propyl.

A method of enzymatically solvolyzing the esterified C-24 hydroxyl group of an epimer of a vitamin D analog having an esterified hydroxyl group at the C-24 stereogenic position thereof comprising the steps of:

• a) providing a solution of the esterified C-24 epimer of a vitamin D analog having a hydroxyl group at C-24 and a solvolysis agent;
• and
• b) contacting the solution with a lipase selected from Alcaligenes sp. lipase and Pseudomonas sp. lipase;
• wherein
• the esterified C-24 epimer is a C-24 ester of a compound of formula general formula III or IX,
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• where R1 and R2 may be the same or different and represent hydrogen or a hydroxy protecting group and R3 is a lower alkyl, cycloalkyl, or aryl group.