DIASTEREO- AND ENANTIO-SELECTIVE CYCLOADDITION AND ENE REACTIONS IN ORGANIC SYNTHESIS

Abstract

1Highly enantioselective C,C-bond formation has been achieved in a predictable manner1.1by Lewis-acid-mediated processes such as intramolecular ene-type reactions (synthesis of (+)-α-allokainic acid), bimolecular Diels-Alder- and 1,4-additions using enoates derived from various chiral alcohols followed by regeneration of the auxiliary group;1.2in the “chiral pool”-synthesis of (-)-α-kainic acid from (S)-(-)-glutamic acid via a thermal intramolecular ene reaction, proving the absolute configuration of the neurophysiologically interesting natural products (-)-α-Kainic acid, (-)-α-allokainic acid and domoic acid.2Intramolecular “magnesium-ene” reactions of 2-alkenyl-magnesium chlorides to olefinic bonds have been systematically studied and applied, as illustrated by2.1the development of a reliable and efficient preparation of 2-alkenyl Grignard reagents using slurries of evaporated magnesium;2.2a synthesis of (±)δ9,12-capnellene using an iterative cyclopentane-annulation based on type-I-ene reactions;2.3a synthesis of the unusual sesquiterpene(±)sinularene via a type-I-reaction;2.4regio-and stereochemical studies of unprecedented type-II-reactions;2.5a direct and highly selective synthesis of the olfactively interesting norsesquiterpene (±)-khusimone exploiting a type-II-reaction.