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The synthesis of the enantiopure C 1 –C 11 fragment of bafilomycin A 1 has been achieved with a 4% overall yield over 18 steps from ( R )-(+)-citronellol. Key steps involve Sharpless asymmetric epoxidation, Miyashita reaction of a γ,δ-epoxymethacrylate with trimethylaluminum in the presence of water, bis-OTMS selective Swern oxidations, Corey–Fuchs alkyne formation, Negishi's carbometalation, and stereoselective formation of the C 2 –C 3 trisubstituted bond of the conjugated diene by a Wittig-type olefination of the α,β-unsaturated C 3 –C 11 aldehyde with the ylide derived from the readily available phosphonium salt [Cl − , Ph 3 P + CH(OMe)COOMe]. |
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