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 α,β-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-β-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.