Determination of Ring Conformation in 1-Benzyl-1, 2, 3, 4-tetrahydroisoquinolines and a New Synthesis of the Chiral Compounds

Abstract

The conformation of the piperideine ring in 1-benzyl-1, 2, 3, 4-tetrahydroisoquinolines was determined as ²H₃ form with a pseudoaxial position of the 1-benzyl group by circular dichroism (CD) spectral comparison with 1-methyl-1, 2, 3, 4-tetrahydroisoquinolines. The chiral center at C-1 of 1, 2, 3, 4-tetrahydroisoquinoline (TIQ) was constructed in an unambiguous manner by applying a new method of TIQ synthesis utilizing the Pummerer reaction as a key step. Enantiomerically pure (R)- and (S)-1-methyl- and 1-benzyltetrahydroisoquinolines (1) were prepared starting from readily available chiral amines (2) in good overall yields.