Precise structure activity relationships in asymmetric catalysis using carbohydrate scaffolds to allow ready fine tuning: dialkylzinc–aldehyde additions
作者:Daniel P. G. Emmerson、Renaud Villard、Claudia Mugnaini、Andrei Batsanov、Judith A. K. Howard、William P. Hems、Robert P. Tooze、Benjamin G. Davis
DOI:10.1039/b309715n
日期:——
carbohydrate ligand structures from a core D-glucosamine scaffold has allowed the evaluation of broad ranging structure activity relationships in ligand accelerated zincate additions to aldehydes, with variations in deltadeltaG+/+(R-S) of up to 5650 J mol(-1) that create opposing senses of asymmetric induction and that are consistent with models based on several ligand X-ray structures and molecular mechanics
Carbohydrate-derived aminoalcohol ligands for asymmetric Reformatsky reactions
作者:Daniel P.G. Emmerson、William P. Hems、Benjamin G. Davis
DOI:10.1016/j.tetasy.2004.11.049
日期:2005.1
Members of a family of functionally and stereochemically diverse D-glucosamine-derived tertiary aminoalcohol ligands have been used to promote the asymmetric Reformatsky reaction. The beta-hydroxyester product tert-butyl 3-phenyl-3-hydroxy-propanoate was obtained enriched in either the (+)-(R) (up to 74% ee) or (-)-(S) (up to 42% ee) enantiomer depending on the choice of ligand. Although the selectivities are modest in absolute terms they represent some the better selectivities obtained to date for this reaction. A H-1 NMR study was conducted to investigate this selectivity and suggested a secondary binding mode between ligand and zinc in addition to the expected N-2, O-3 coordination. (C) 2004 Elsevier Ltd. All rights reserved.