Enantioselective Total Synthesis of atrans-Hydrindane Rings/Side-Chain Building-Block of Vitamin D− Asymmetric Induction in an Acid-Catalyzed Conjugate-Addition Reaction
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
1,3- versus 1,4-Asymmetric induction in Mukaiyama–Michael additions of optically active ketene acetals to 2-methylcyclopent-2-en-1-one: a remarkable inversion of facial selectivity
TrSbCl6-catalyzed addition of selected optically active ketene acetals to 2-methylcyclopent-2-en-1-one for steroid synthesis is described. Inversion of facial selectivity in 1,3- and 1,4-asymmetricinduction was observed.
The 1α,25-dihydroxyvitaminD3 enantiomer was synthesized and examined in biological tests. The ring A precursor was prepared from vitamin D2 employing the Mitsunobu reaction for inversion of the configuration at C-3 and SeO2 hydroxylation at C-1. The CD rings-side chain portion was synthesized from an optically active hexanoic acid derivative using diastereoselective tandem Mukaiyama–Michael addition
Diastereoselective Approaches to trans-Hydrindane Derivatives − Total Synthesis of 8-(Phenylsulfonyl)de-A,B-cholestane Precursors to 25-Hydroxyvitamin D3
The total diastereoselectivesynthesis of the C,D rings/side chain building block for the synthesis of 1α,25-dihydroxyvitamin D3 is described. Two tandem Mukaiyama−Michael additions involving silylated ketene acetals derived from tert-butyl 6-methylhept-5-enethioate or tert-butyl 6-methylhept-6-enethioate, 2-methylcyclopent-2-en-1-one, and 1-(phenylthio)but-3-en-2-one afforded the corresponding intermediates
Multikilogram Synthesis of a Potent Dual Bcl-2/Bcl-x<sub>L</sub> Antagonist. 2. Manufacture of the 1,3-Diamine Moiety and Improvement of the Final Coupling Reaction
paper describes the synthesis of kilogram quantities of the sulfonamide moiety 3 involved in a coupling reaction with acid moiety 2 to provide batches of drug candidate 1 for preclinical studies and first-in-human clinical trials. A first approach relying on a chiral separation furnished the desired enantiomer of 1,3-diamine 20, precursor of sulfonamide 3. An enantiomeric synthesis of 20 using the Ellman’s