Three new naphthyldihydroisoquinoline alkaloids from Ancistrocladus tectorius.

Three new 5--1'-linked naphthyldihydroisoquinoline alkaloids (1-3) have been isolated from the organic extract of Ancistrocladus tectorius. The gross structures of the compounds have been established using 1D and 2D NMR spectroscopy and difference NOE experiments. The absolute stereochemistry of 1, 2, and 3 was determined from CD spectral comparison and chemical degradation. Evidence is presented to show that two of the compounds exist exclusively in the keto form at C-8 of the isoquinoline system (2b, 3b).