We have recently reported the catalytic asymmetric allylation of a cyclic imine by allyltrimethoxysilane and catalytic amounts of (S)-tol-binap and CuCl. The reaction was examined to improve the yield and selectivity using a 3,4-dihydroisoquinoline as a substrate. A chiral 1-allyl derivative was obtained in 97% yield and 82%ee by use of 9 mol% DTBM-SEGPHOS and 6 mol% CuF2. The adduct thus obtained was applied to the total synthesis of schulzeine A. Schulzeine A is an alfa-glucosidase inhibitor, and consists of two fragments of an isoquinoline nucleus and C28 fatty acid. The allyl adduct was oxidized to an aldehyde, which was further transformed to an alkene by HWE reaction. The alkene was reduced using the H2-Rh-MONOPHOS catalyst to give correct stereocenters of the isoquinoline moiety.
