Evidence for C(1)–N(2) bond scission in the isomerization of cis-1,3-disubstituted Nb-benzyl-1,2,3,4-tetrahydro-β-carbolines into their trans diastereomers under acidic conditions

Abstract

When cis diastereomer 13a was stirred in CF₃CO₂D the trans isomer 13b ws isolated in 90% yield, while treatment of 13a with CF₃CO₂H–NaBH₄ provided a mixture of the C(1)–N(2) cleaved product 14 and the trans isomer 13b; this provides the best evidence to date that scission of the C(1)–N(2) bond occurs during epimerization of cis-1,3-disubstituted 1,2,3,4-tetrahydro-β-carbolines such as 13a into their trans isomers 13b.