Stereoselective synthesis of (25R)-26-fluoro-5-cholesten-3β,25-diol 3-acetate from methyl 3β-hydroxy-5-cholenoate
摘要:
A stereoselective synthesis of (25R)-26-fluoro-5-cholesten-3-beta,25-diol 3-acetate (1) from methyl 3-beta-hydroxy-5-cholenoate (2) is presented. Formation of the asymmetric center at C-25 was accomplished by application of the Sharpless epoxidation methodology from 6-beta-methoxy-3-alpha,5-cyclo-5-alpha-cholest-25(27)-en-26-ol (7). Substitution of the C-27 hydroxyl group of (25R)-6-beta-methoxy-3-alpha,5-cyclo-25,26-epoxy-5-alpha-cholestan-27-ol (8) by a fluorine atom, via mesylate derivative, and subsequent reduction of the oxirane ring with LiAIH4 afforded (25R)-6-beta-methoxy-26-fluoro-3-alpha,5-cyclo-5-alpha-cholestan-25-ol (16). Deprotection of the 3-beta-hydroxy-5(6)-en system in 16 with BF3.Et2O/acetic acid yielded the title compound 1.
Stereoselective synthesis of (25R)-26-fluoro-5-cholesten-3β,25-diol 3-acetate from methyl 3β-hydroxy-5-cholenoate
摘要:
A stereoselective synthesis of (25R)-26-fluoro-5-cholesten-3-beta,25-diol 3-acetate (1) from methyl 3-beta-hydroxy-5-cholenoate (2) is presented. Formation of the asymmetric center at C-25 was accomplished by application of the Sharpless epoxidation methodology from 6-beta-methoxy-3-alpha,5-cyclo-5-alpha-cholest-25(27)-en-26-ol (7). Substitution of the C-27 hydroxyl group of (25R)-6-beta-methoxy-3-alpha,5-cyclo-25,26-epoxy-5-alpha-cholestan-27-ol (8) by a fluorine atom, via mesylate derivative, and subsequent reduction of the oxirane ring with LiAIH4 afforded (25R)-6-beta-methoxy-26-fluoro-3-alpha,5-cyclo-5-alpha-cholestan-25-ol (16). Deprotection of the 3-beta-hydroxy-5(6)-en system in 16 with BF3.Et2O/acetic acid yielded the title compound 1.