Carbohydrate-derived aminoalcohol ligands for asymmetric Reformatsky reactions

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 β-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 1H 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. © 2004 Elsevier Ltd. All rights reserved

Carbohydrate-derived amino-alcohol ligands for asymmetric alkynylation of aldehydes.

[reaction: see text] Conformationally restricted amino alcohols based on carbohydrate scaffolds provide flexible and fine-tuneable libraries that greatly expand the range of ligands available in the Zn(OTf)(2)-mediated addition of alkynes to aldehydes, in some cases with very high stereoselectivities

Precise structure activity relationships in asymmetric catalysis using carbohydrate scaffolds to allow ready fine tuning: dialkylzinc-aldehyde additions.

The ready construction of 24 stereochemically and functionally diverse 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 analysis. Factorial analysis of enantioselectivity using key dihedral angles and steric volume on N-2 also highlight the potential for the use of factorial design in ligand construction