Synthesis of Chiral (Indol‐2‐yl)methanamines and Insight into the Stereochemistry Protecting Effects of the 9‐Phenyl‐9‐fluorenyl Protecting Group

Abstract

Tetrahydro‐β‐carbolines, a privileged structural feature in natural products and pharmaceutically active compounds, has been the cause for considerable research interest, spanning many decades. Herein is reported the synthesis of the structurally closely related compounds denoted as (indol‐2‐yl)methanamines, in 99 % ee using amino acid starting materials, coupled with a 9‐phenyl‐9‐fluorenyl (Pf) protecting group strategy. Furthermore a conformational study of Pf‐protected α‐amino carbonyl compounds were undertaken by means of DFT refined molecular mechanics calculation, X‐ray crystallography measurements and NMR experiments in order to elucidate the stereochemical protecting properties induced by the Pf group.