Vinyl and alkynyl pyrimidines as Michael acceptors: An approach to a cylindrospermopsin substructure

Abstract

Vinyl pyrimidine 9 and alkynyl pyrimidine 24 undergo base-mediated intramolecular conjugate addition reactions in which a carbamate and a urea, respectively, behave as nitrogen nucleophiles. The cyclic carbamate derived from 9 was converted to 11 via a metalation-oxidation reaction in which 2-phenylsulfonyl-3-phenyloxaziridine behaves as a hydroxylation reagent. The cyclic urea derived from 24 was converted to cylindrospermopsin substructure 30 using dimethyldioxirane to introduce the C7 hydroxyl group.