Asymmetric Dihydroxylation onto the a,b-Unsaturated Carboxylic Ester Derivatives of Camptothecin
摘要:
Dihydroxyalkanoic ester derivatives (4a,b) and (5a,b) of 20S-camptothecin (1) were diastereoselectively synthesized by exploiting osmium-catalyzed asymmetric dihydroxylation based on the Sharpless procedure. The absolute configuration of the newly formed chiral centers, the 2' and 3' positions of the 20-alkanoyl side chain of 4a,b and 5a,b was determined by the chemical correlation with the known chiral dihydroxyalkanoic acids.
Process Research of (<i>R</i>)-Cyclohexyl Lactic Acid and Related Building Blocks: A Comparative Study
作者:Thomas Storz、Peter Dittmar、Pierre François Fauquex、Philippe Marschal、Willy Urs Lottenbach、Heinz Steiner
DOI:10.1021/op030202q
日期:2003.7.1
enantiomeric resolution of the resulting, racemic phenyllacticacid via diasteromeric salt formation and phenyl ring hydrogenation; (D) enantioselective dihydroxylation of a cinnamate ester, followed by hydrogenation of the benzylic hydroxy group and the aromatic nucleus; (E) enantioselective biocatalytic reduction of phenylpyruvic acid, followed by phenyl ring hydrogenation. The development of (2R)-2
A General Asymmetric Synthesis of <i>syn</i>- and <i>anti</i>-β-Substituted Cysteine and Serine Derivatives
作者:Chiyi Xiong、Wei Wang、Victor J. Hruby
DOI:10.1021/jo011172x
日期:2002.5.1
syn-beta-substituted cysteine and serinederivatives. In this approach, the key intermediates, > 94% enantiomerically pure cyclic sulfates 3 and aziridines 7, were prepared from alpha,beta-unsaturated esters 1, employing the Sharpless asymmetric dihydroxylation. The high regio- and stereoselective ring-opening reactions of cyclic sulfates and aziridines provided enantiomerically pure beta-substituted cysteine and serine