61(P1-9) シクロプロペノン抗生物質ペニトリシンおよびその誘導体の合成(ポスター発表の部)

概要

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Deprotonation of a cyclopropenone ketal (5) with BuLi in THF generates a lithio cyclopropene 6 which is stable at low temperatures in the presence of HMPA or TMEDA. Transmetalation with ZnCl_2 gives the corresponding zinc species 7. These metalated cyclopropenone ketals react with a variety of electrophiles to give mono-substituted cyclopropenone ketals 3 in high yield, which upon mild acidic hydrolysis give a variety of 2-substituted cyclopropenones 4 in high yield. Repetition of the alkylation/hydrolysis sequence gives 2,3-disubstituted cyclopropenones as well. The reaction of lithio cyclopropene 6 with carbonyl compounds followed by acidic hydrolysis gives α-hydroxy cyclopropenones in high yield, providing an efficient access to the novel cyclopropenone antibiotic penitricin (1). The method also allows preparation of a number of penitricin congeners. Examination of the antibiotic and cytotoxic activities of these compounds indicated that the hydroxyl group adjacent to the cyclopropenone ring is indispensable for the antibiotic activities. In order to probe the effects of the hydroxyl group, molecular structures and electronic properties of penitricin and its protonated structures have been studied with molecular orbital calculations using ab initio (HF/3-21G) and semiempirical methods (AM1).
天然有機化合物討論会の論文
1989-09-17