Selective J-resolved HMBC, an efficient method for measuring heteronuclear long-range coupling constants

An efficient pulse sequence for measuring long-range C-H coupling constants (J(C-H)) named selective J-resolved HMBC has been developed by replacing a (1)H 180 degrees pulse with a selective (1)H 180 degrees pulse and the HMBC pulse scheme with the constant time (CT) HMBC employed in the J-resolved HMBC pulse sequence that we reported previously. The novel pulse sequence providing only long-range J(C-H) cross peaks for easy and accurate analysis enables to overcome disadvantages of the previous HMBC-based pulse sequences (J-resolved HMBC-1) along with maintaining high sensitivity. The efficiency of measuring long-range J(C-H) using the proposed pulse sequence has been demonstrated in applications to the complicated natural products, portmicin and monazomycin. Copyright (C) 2009 John Wiley & Sons, Ltd.