Novel Bicylic Donors for the Synthesis of 2-Deoxy-β-Glycosides
作者:Richard W. Franck、Cecilia H. Marzabadi
DOI:10.1021/jo971934h
日期:1998.4.1
Novel bicyclic glycosyl donors have been prepared by the cycloaddition reaction of glycals with 3-thiono-2,4-pentanedione 17 followed by methylenation of the resulting ketone. Treatment of the heterocyclic donors with triflic acid in the presence of a variety of alcohol accepters leads to the formation of beta-glycosides in good yields and with excellent stereoselectivities. Desulfurization of the C-2 carbon-sulfur bonds gives the corresponding 2-deoxy-beta-glycosides. This method has been extended to the synthesis of glycosidic linkages found in the aureolic acid antibiotics. Tetra-N-butylammonium triflate proved to be a useful additive in these glycosylation reactions, suggesting an important role for triflate anion in stabilizing intermediates which are formed.
Chromomycin A3 as a Blueprint for Designed Metal Complexes
作者:Domingos J. Silva、Daniel Kahne、Christina M. Kraml
DOI:10.1021/ja00085a063
日期:1994.3
Determining Absolute Configuration in Flexible Molecules: A Case Study
作者:Kimberly Musa Specht、Joonwoo Nam、Douglas M. Ho、Nina Berova、Rama K. Kondru、David N. Beratan、Peter Wipf、Robert A. Pascal,、Daniel Kahne
DOI:10.1021/ja0104406
日期:2001.9.1
Assigning absoluteconfiguration of molecules continues to be a major problem. Determining absoluteconfiguration in conformationally flexible systems is challenging, even for experts. Here, we present a case study in which we use a combination of molecular modeling, solution NMR, and X-ray crystallography to illustrate why it is difficult to use solution methods alone for configuration assignment
分配分子的绝对构型仍然是一个主要问题。确定构象灵活系统中的绝对构型具有挑战性,即使对专家来说也是如此。在这里,我们展示了一个案例研究,其中我们结合使用分子建模、溶液 NMR 和 X 射线晶体学来说明为什么很难单独使用溶液方法进行配置分配。对于所检查的案例,计算和实验旋光色散 (ORD) 数据的比较提供了分配绝对配置的最直接的方法。