Synthesis of Alkaloids of Galipea officinalis by Alkylation of an α‐Amino Nitrile

A new synthetic approach directed towards the synthesis of naturally occurring 2‐alkyl‐tetrahydroquinolines is described. The C–C bonds in the α position relative to the nitrogen atom were formed by the reversal of the polarity of the C=N bond of α‐amino nitrile 6 , which was prepared electrochemically from 1‐(phenylethyl)‐tetrahydroquinoline. A NaBH 4 ‐mediated reductive decyanation process furnished benzylic amines 16a – d as mixtures of diastereomers (50–60 % de ). The catalytic hydrogenolysis of these amines was performed in the presence of Pearlman's catalyst to give the tetrahydroquinolines 17a – d in yields ranging from 70 % to 95 %. Methylation of the free nitrogen atom afforded the title compounds 1 – 4 in 70–90 % yields.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)