Lyngbyastatin 1 and Ibu-epilyngbyastatin 1: Synthesis, Stereochemistry, and NMR Line Broadening
作者:Ruoli Bai、Robert B. Bates、Ernest Hamel、Richard E. Moore、Pichaya Nakkiew、George R. Pettit、Bilal A. Sufi
DOI:10.1021/np020117w
日期:2002.12.1
lyngbyastatin 1-Ibu-epilyngbyastatin 1 mixture combined with NMR and molecular modeling studies proved that natural lyngbyastatin 1 was only one Ibu epimer rather than a mixture of both and that the configuration of this epimer in the Ibu unit was R. The substance isolated with lyngbyastatin 1 was Ibu-epidolastatin 12. The extreme broadness in the proton NMR spectra of lyngbyastatin 1 and Ibu-epidolastatin 12
lyngbyastatin 1-Ibu-epilyngbyastatin 1混合物的合成与NMR和分子模型研究相结合证明,天然lyngbyastatin 1只是一个Ibu差向异构体,而不是两者的混合物,并且该差向异构体在Ibu单元中的构型是R.用lyngbyastatin 1分离的物质是Ibu-epidolastatin12。由于围绕Ibu-Ala酰胺键旋转,lyngbyastatin 1和Ibu-epidolastatin 12的质子NMR光谱中的极宽光谱正在交换加宽。这是由于(1)此键的顺式和反式之间的能量差异小;(2)这些形式之间的构象存在实质性差异;以及(3)与大多数酰胺键相比,它们之间的势垒降低了(由于位阻)。