BASHD-J-resolved-COSY: a new method for measuring proton-proton spin coupling constants of multiplet signals

An effective pulse sequence for measuring HH coupling constants, named BASHD-J-resolved-COSY, has been developed. In the spin systems such as CHACHB(CH3)CHC, a methine proton HB splits into a multiplet owing to several vicinal couplings, resulting in attenuation of its cross-peak intensity. Therefore, the measurements of 3JHH with respect to HB are generally difficult in the E-COSY-type experiments. With the aim of accurate measurements of 3JH-H in such a spin system, we have developed a new pulse sequence, which selectively decouples the secondary methyl group. The proposed pulse sequence provides the simplified cross-peak patterns, which are suitable for reliable measurements of 3JH-H in a complicated natural product. Copyright (c) 2012 John Wiley & Sons, Ltd.