In the course of our investigation of biologically interesting compounds, we isolated altersolanol A (1), alterorriols D (2), E (3), F (4), and G (5) from Pleospora sp. Altersolanol A (1) is a monomer of 2 and 4. Since considerable difference between 1H NMR spectrum of our alterporriols and those in literature, stereochemistry of 1 was also further determined. Although "W" shaped long range coupling between C1H and C3H in the acetonide of 1, suggesting cis-orientation for these protons, X-ray studies revealed our comound has identical structure of the in the literature and the s tereochemistry of those must be trans-orientation. We also observed dimerization of the acetonide from of 1 giving the corresponding dimmers (10). Since the CD spectra of 2 and 3 were axisymmetrical each other, these assumed to be atropiomers. Interestingly benzoylation of C1 hydroxy group of 10 resulted in a shielding of very far located C7-OMe group. Since this chemical shift alteration was not observed in the monomer, we assumed the methoxy group, being shifted by the benzoylation of C1OH, should be involved in the other naphthoqunone ring. These discussions led us assign the atropchemistry of 2 as M-isomer, while that of 3 should be P. Pleospora sp. also provided alterporriols F (4) and G (5), the C4-deoxy forms of 2 and 3. In the symposium, the detail of their NMR spectrum, biosnthetic assumption based on our observations, and theoretical CD calculations of 2 and 3 also would be discussed.
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