Patent ID: 8129173

Claim:
A method of selectively enzymatically esterifying the C-24 hydroxyl group of one epimer in a mixture of C-24 epimers of a compound of general formula III or IX: where R 1 and R 2 may be the same or different and independently represent hydrogen, or hydroxy protecting group, and R 3 is cyclopropyl or isopropyl, comprising the steps of: a) providing a solution of said mixture of C-24 epimers and an esterifying agent in an organic solvent, wherein the esterifying agent is selected from the group consisting of alkyl and vinyl esters; and b) contacting the solution with a lipase, wherein the lipase is Alcaligenes sp. lipase or Psudomonas sp lipase; wherein at least one of R 1 and R 2 is —H; and wherein the epimer that is selectively enzymatically esterified is one having an R absolute configuration.