Stereochemistry of bisbenzylisoquinoline N-oxides. Calafatine 2α-N-oxide and calafatine 2β-N-oxide
Abstract
The diastereoisomeric alkaloids calafatine 2α-N-oxide (2) and Calafatine 2β-N-oxide (3) have been obtained from Berberis buxifolia Lam. (Berberidaceae). The stereochemistry at the N-oxide centres was determined by n.m.r. nuclear Overhauser difference studies.