Comparative cotton effects of steroidal 2,4-dienes and related trienes: origin of the folded conformation in levopimaric acid
作者:Albert W. Burgstahler、Jacek Gawronski、Theodore F. Niemann、Benjamin A. Feinberg
DOI:10.1039/c29710000121
日期:——
The decreased intensity of the positive Cotton effects of a 9α-methyl- and a 19-nor-steroidal 2,4-diene compared to those of other steroidal 2,4-dienes suggests that the peculiar B/C folded conformation in levopimaric acid (negative Cotton effect) is caused by relief of a 1,3-diaxial repulsion between the C-10 angular methyl group and the 11β-hydrogen, probably enhanced by C-4 methyl buttressing, which
与其他甾体2,4-二烯类相比,9α-甲基和19-去甾体2,4-二烯对棉花的正效应降低的强度表明左旋海马酸中独特的B / C折叠构象(负Cotton效应)由C-10角甲基组之间的1,3- diaxial斥力的浮雕引起和11 β -氢,可能是由C-4甲基拱托,将所得的9α-和11α的食增强-氢不足以取代。