Biosynthesis of naphthylisoquinoline alkaloids:: synthesis and incorporation of an advanced 13C2-labeled isoquinoline precursor

Biosynthetic studies on naphthylisoquinoline alkaloids involving a specifically [1,1,-13 C-2]-labeled dihydroisoquinoline 7 are described. The synthesized precursor 7 was fed to callus cultures of Triphyophyllum peltatum and the isolated secondary metabolites were characterized by spectroscopic methods (H-1, C-13 NMR, and INADEQUATE experiments). The unambiguous incorporation of the precursor into dioncophylline A and two minor naphthylisoquinolines, together with the formation of the labeled corresponding trans-configured tetrahydroisoquinoline, proves the implication of such advanced intermediates in the proposed biosynthetic pathway of naphthylisoquinoline alkaloids. (c) 2006 Elsevier Ltd. All rights reserved.