Asymmetric Epoxidation of <i>cis</i>-Alkenes Mediated by Iminium Salts: Highly Enantioselective Synthesis of Levcromakalim

Abstract

[reaction: see text] A range of cis-substituted olefins has been epoxidized with a new dihydroisoquinolinium salt catalyst, using tetraphenylphosphonium monoperoxysulfate as the stoichiometric oxidant, giving ee's of up to 97%. The reaction has been used as the key step in an enantioselective synthesis of the antihypertensive agent levcromakalim.