BASHD‐ J ‐resolved‐HMBC, an efficient method for measuring proton–proton and heteronuclear long‐range coupling constants

Natural products often possess various spin systems consisting of a methine group directly bonded to a methyl group (e.g. –CH a –CH b (CH 3 )–CH c –). The methine proton H b splits into a broadened multiplet by coupling with several vicinal protons, rendering analysis difficult of n J C–H with respect to H b in the J ‐resolved HMBC‐1. In purpose of the reliable and easy measurements of n J C–H and n J H–H in the aforesaid spin system, we have developed a new technique, named BASHD‐ J ‐resolved‐HMBC. This method incorporates band selective homo decoupled pulse and J ‐scaling pulse into HMBC. In this method, high resolution cross peaks can be observed along the F 1 axis by J ‐scaling pulse, and band selective homo decoupled pulse simplified multiplet signals. Determinations of n J C–H and n J H–H of multiplet signals can easily be performed using the proposed pulse sequence. Copyright © 2013 John Wiley & Sons, Ltd.