trans-1,3-dithiane-1,3-dioxide; a chiral acyl anion equivalent. Enantioselective synthesis of α-hydroxy- carboxylic acids, esters, amides and ketones
作者:Varinder K. Aggarwal、Abraham Thomas、Steffen Schade
DOI:10.1016/s0040-4020(97)01010-7
日期:1997.12
transformations of thioesters to various α-hydroxy carboxylic acid derivatives (acids, esters, amides) without racemisation have been achieved. The approach resulted in the synthesis of the dimethyl ether of (R)-(−)-3,4-dihydroxymandelic acid in its naturally occurring form. Addition of dibutyl cuprate (derived from BuMgBr and Cu(I)Br) to the thioester gave the corresponding ketone in high yield and again without
on the asymmetric induction as well as catalyst efficiency. The chiral centers in AA' and AA' amino acid residues in 5 were also found to have some influence on the catalytic asymmetric induction. Possible mechanism which can accommodate these effects are discussed. Asymmetricreduction of RCOCO-AA-OMe (13) via hydrosilylation was carried out to give chiral depsipeptide units. The asymmetric hydrogenation
SYNTHESIS OF CHIRAL DEPSIPEPTIDE BUILDING BLOCK VIA ASYMMETRIC HYDROSILYLATION
作者:Jin-shui Yao、You-shi Wu
DOI:10.1081/scc-120002401
日期:2002.1.1
ABSTRACT Asymmetric hydrosilylation of N-(α-ketoacyl)-α-amino esters was performed, catalyzed by rhodium(I) complex of chiral 2-(2-pyridyl)-4-carbomethoxy-1,3-thiazolidine or Rh(PPh3)3Cl. The N-(α-hydroxyacyl)-α-amino esters were synthesized in high stereoselectivity.
Asymmetric hydrogenation of N-(α-ketoacyl)-α-amino esters with Cydiop–rhodium(I) complex catalysts produced optically active N-(α-hydroxyacyl)-α-amino esters in high optical yields, which may be useful as building blocks of depsipeptides. Almost no influence of the chiral center of substrate was observed.
have been prepared by various synthetic methods. Rhodium(I) complexes of 3 and 8 showed high catalytic activity for hydrogenation of various kinds of prochiral ketones, which were reduced smoothly to the corresponding optically active hydroxy compounds, under hydrogen at atmospheric pressure and ambient temperature. The neutral rhodium(I) complexes (diphosphine-RhN) hydrogenated α-ketoamides and α-ketopantolactone