A novel and practical route to A-ring enyne synthon for 1α,25-dihydroxyvitamin D3 analogs: Synthesis of A-ring diastereomers of 1α,25-dihydroxyvitamin D3 and 2-methyl-1,25-dihydroxyvitamin D3

for a variety of A-ring analogs of 1α,25-dihydroxyvitamin D3 (1), was developed. This novel method led to an improved synthesis of the A-ring diastereomers of 1, the compounds 13–15, and synthesis of the new analogs, 2-methyl-1,25-dihydroxyvitamin D3 (4) with its all possible diastereomers. The biological evaluation of the 2-methyl analogs showed the ααβ-isomer to be more potent than 1.