Two-dimensional correlation of directly and remotely connected transitions by z-filtered COSY

An expt. is described which uses essentially the same pulse sequence as 2-dimensional (2D) exchange spectroscopy (NOESY), but where the flip angles of the 2 pulses that precede and follow the mixing period tm are small (b .simeq.20 Deg). Use of a NOESY-like sequence is proposed, where tm is chosen to be too short to allow exchange phenomena to play a role, and serves merely to eliminate coherence-transfer pathways through single-, multiple-, and zero-quantum coherences, while retaining only transfer processes by way of longitudinal magnetization, in the manner of z filters. Illustrative 2D z-filtered correlation spectra (z-COSY) showing coherence transfer between directly connected transitions (q = 0) of the 4 arom. protons of salicylic acid in CDCl3 with 10% DMSO-d6. [on SciFinder (R)]