Enantioselective Syntheses of Pachastrissamine and Jaspine A via Hydroxylactonization of a Chiral Epoxy Ester

Abstract

A new enantioselective total synthesis of pachastrissamine (jaspine B) was achieved from a known α,β-unsaturated aldehyde by utilizing Córdova’s asymmetric epoxidation as the chirality-inducing step. The 2,3-cis stereochemistry of pachastrissamine was established via intramolecular epoxide ring opening of a γ,δ-epoxy-α,β-unsaturated ester intermediate coupled with oxy-Michael cyclization. Treatment of pachastrissamine with tetrahydro-2-furanol under acidic conditions led to smooth oxazolidine ring formation, furnishing jaspine A in a high yield.