Enantioselective total synthesis of a trans-hydrindane rings/side-chain building-block of vitamin D - Asymmetric induction in an acid-catalyzed conjugate-addition reaction

Article abstract of DOI:10.1002/ejoc.200300611

For the enantioselective total synthesis of 1α,25-dihydroxyvitamin D₃ (3), we have developed an enantioselective approach to the "northern" portion building-block 8, starting from the optically active hexanoic acid derivative 44, 2-methylcyclopent-2-en-1-one (10) and 1-(phenylthio)but-3-en-2-one (9). The steric course of the addition reaction of homochiral (S)-ketene acetals 28, 40, 44 and 58 with 10 was examined. We found that in the cases of 28, 44 and 40, the reactions occur with high simple and induced (facial) diastereoselectivities. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.