21 新規不斉転写エン反応の開発およびアントラサイクリン合成への応用(口頭発表の部)

概要

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A highly enantio-selective ene reaction was developed on the bases of chirality transfer. An optically pure ene substrate (S)-3-(tert-butyldimethylsiloxy)-2-(ethylthio)-1-butene 1b was prepared in three steps from (S)-ethyl lactate. Under the influence of Me_2AlCl, the reactions of 1b with aromatic, aliphatic, or α, β-unsaturated aldehydes afforded the optically active adducts 2 in high ee. Based on these results, an efficient synthetic method of an optically pure anthracyclinone precursor was developed. The ene reaction of aldehyde 10 with 1c afforded the almost enantiomerically pure adduct 11 in high yield. Diol 12 was prepared through regioselective lithiation and hydroxymethylation. Construction of A-ring to give ketone 15 was performed by trichloro-acetylation of 12 followed by treatment with Me_2AlCl. Diastereoselective oxidation of enol silylether 18, which was obtained through reductive silylation of α-(methylthio)ketone, afforded the anthracyclinone precursor 19.
天然有機化合物討論会の論文
1992-09-10