Conformational analysis of A and B rings in 2-, 4-, and 6-bromosubstituted steroidal 4-en-3-ones by nuclear magnetic resonance
作者:R. Sridharan、Umesh R. Desai、R. Madhusudhan Rao、Girish K. Trivedi
DOI:10.1016/0039-128x(93)90064-t
日期:1993.4
distortion in the chair form of the B ring. Conformational preferences of A and B rings are not found to be influenced by transmission effect of a side chain or oxygenated ring system. Temperature-dependent NMR studies indicate the reduced conformational flexibility of the A ring for 2 alpha-bromosubstituted steroids. Complete assignment of the 13C and 1H resonances of two of the steroids studied (3 and
通过协同应用高分辨率一维和二维核磁共振 (NMR) 技术,如同核和异核相关联,研究了四种不同功能化溴取代 4-en-3-one 类固醇中 A 和 B 环的构象偏好光谱、瞬态和稳态 nOe 光谱、温度相关的化学位移变化,以及改进的 Karplus 方程的应用。研究的类固醇包括 6 beta-bromocholest-4-en-3-one (3), 4,6 beta-dibromocholest-1,4-dien-3-one (2), 2 alpha,4,6 beta-tribromocholest- 4-en-3-one (1) 和 (25R)-2 alpha,6 beta-dibromospirost-4-en-3-one (4)。类固醇 1-4 是通过酸催化或自由基溴化从适当的 4-en-3-one 类固醇制备的。该研究深入了解了导致这些溴代类固醇的 A 和 B 环构象偏好的因素。2 alpha