The first asymmetric totalsynthesis of (+)-jatrophalactam was reported, which unambiguously determined the absolute configuration of the titled natural product. The key features entail a conformationally controlled cyclopropanation, a Meldrum’s acid adduct-engaged macrolactam formation, and a Pd(II)-mediated oxidative cyclization.
A concise and convergent route to (+)-polyanthellin A is presented. This synthesis features a diastereoselective cyclopropane/aldehyde [3+2] cycloaddition to install the hydroisobenzofuran core. The use of MADNTf(2) as a potent, bulky Lewis acid was essential to allow a labile B-silyloxy aldehyde to be used in the cycloaddition. Other key steps include a ring-closing metathesis and a selective olefin oxidation
Xu, Daqiang; Crispino, Gerard A.; Sharpless, K. Barry, Journal of the American Chemical Society, 1992, vol. 114, # 19, p. 7570 - 7571
作者:Xu, Daqiang、Crispino, Gerard A.、Sharpless, K. Barry
DOI:——
日期:——
Syntheses of 5a‘-<i>h</i><i>omo</i>-Vinblastine and Congeners Designed to Establish Structural Determinants for Isolation of Atropisomers
作者:Martin E. Kuehne、Scott D. Cowen、Feng Xu、Linda S. Borman
DOI:10.1021/jo000249z
日期:2001.8.1
The syntheses of 5a'-homo-vinblastine (3a) and its C-20' methyl congener 62a were achieved. In contrast to vinblastine, these compounds did not allow isolation of atropisomers because of their lower conformational inversion barrier. However, annelation of a six-membered ring to the conformationally mobile D'-piperidine ring provided an isolated atropisomer 81a, which could be converted to its lower energy conformation 65a on heating. The 5a'-homo-vinblastine congeners 3a, 62a, and 65a showed vinblastine-like inhibition of tubulin polymerization and cytotoxicity to L1210 leukemia cells, albeit at lower potency for the latter activity, than that found with the corresponding compounds in the vinblastine series.