A nuclear magnetic resonance study of the diastereoisomer complexes formed between a terguride derivative and naproxen

Abstract

Abstract 1 H NMR (600 MHz) measurements of chemical shift changes were made in acidified (DCI) CD 3 OD/D 2 O 1:9 v/v equimolar solutions of (S)‐ and (R,S)‐6‐methoxy‐α‐methyl‐2‐naphthaleneacetic acid (naproxen) in the presence of 1‐(3‐aminopropyl)‐(5R,8S,10R)‐terguride (AMP‐TER). The most significant bonding interactions concurring to the formation of diastereoisomer complexes are seen as chemical shifts in proximity to the positively charged nitrogen N(6)‐CH 3 and of H(12), H(13), H(14) protons of the ergoline skeleton, both the adducts having an electrostatic term and different π–π stabilizing interactions. Chemical shift data exclude any contribution of the aminopropyl chain to the chiral recognition mechanism. These findings provide an experimental basis for the enantiodiscriminative process accounting for the observed chromatographic resolutions of arylcarboxylic acids on chiral stationary phases derived from AMP‐TER. © 1994 Wiley‐Liss, Inc.