Asymmetric C-C bond formation via Darzens condensation and Michael addition using monosaccharide-based chiral crown ethers

Liquid-liquid phase asymmetric Darzens condensations were promoted by D-glucose- and D-mannose-based crown ethers. The corresponding aromatic and heteroaromatic alpha,beta-epoxyketones were obtained with moderate to high enantioselectivities (up to 96%) as well as diastereoselectivities (up to 98:2) under mild reaction conditions. The absolute configurations of several of the epoxyketones were determined by single crystal X-ray analysis. The Michael additions of diethyl acetylaminomalonate to trans-beta-nitroalkenes were carried out in a solid-liquid two-phase system in the presence of a D-glucose-based crown catalyst with up to 99% ee. (c) 2011 Elsevier Ltd. All rights reserved.