42 新抗生物質Ascofuranone分子の絶対配置

抄録

Molecular structure and absolute configuration of 4-o-ethyl ascofuranone (C_<23>H_<28>O_5Cl・C_2H_5) were determined by X-ray crystal structure analysis. Crystal structure was solved by the multisolution method. Dihydro-2,2-dimethyl-furan-3-one ring in the molecule adopts an envelope conformation, and the spatial configuration around the asymmetric carbon on the ring is Sinister according to the notation by Cahn, Ingold and Prelog. ORD and CD spectra were consistent with the ketone octant rule which predicted negative Cotton effect for the carbonyl n-π transition. Proton NMR spectra indicated that the ring was rigid, and its conformation in the solution was approximately identical to that in the crystal. All these results are the first stereochemical data on dihydro-2,2-dimethyl-furan-3-one ring in natural product.