33 セスターテルペン,セファロン酸の構造

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The structure of ophiolobin, fungal metabolite from Ophiobolus miyabeanus was established. Subsequently, the structure of zizanin-A and -B, isolated from Helminthosporium zizaniae, were eluoidated by chemical correlation. These compounds, which have O_<25> carbon skeleton were classidied as Sester-terpenoid. On the other hand, we have been engaged the structural studies of helvolic acid which is protolanostan type compound isolated from Cephalosporium caerulans. Recently, this fungus is found to produce new antibiotic named as cephalonio acid which shows weak activity against Staphylococcus aureus. Cephalonic acid, m.p. 139-140°, [α]_D76.2°showed UV absorption maximum at 258 mμ (logε, 4.06). The mass spectrum confirmed the empirical formula C_<25>H_<36>O_4. The IR spectrum indicates the presence of carboxyl group, carbonyl group and olefinic linkage. The n.m.r, showed the presence of five methyls, an olefinic proton at 5.02, a methine proton on the carbon atom bearing hydroxyl group at 5.02, a methine proton at 4.38, and α-proton of αβ-unsaturated carbonyl system at 6.05. The complete structure of cephalonic acid uncluding its absolute configuration was solved by three dimensional X-ray crystallography of the bromoacetyl derivative. The results revealed that the structure of cephalonic acid was as expressed by I. Hydrogenation of methyl cephalonate II with Pt catalyst gave III, IV and V, while with Pd/C afforded Vi as a sole product. The UV spectra of I and VI were identical with those of VIII and VII respectively. The mass spectrometric fragmentation are discussed briefly.
天然有機化合物討論会の論文
1966-09-15

33 セスターテルペン,セファロン酸の構造

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