1D DETERMINATION OF LONG-RANGE HETERONUCLEAR COUPLING-CONSTANTS BY GRADIENT-ENHANCED SIMBA

Two H-1-detected one-dimensional gradient enhanced experiments and cor responding reference experiments are proposed for the measurement of h eteronuclear long-range (II)J(CH) coupling constants in organic molecu les. These experiments use inverse detection and selective carbon exci tation, provide excellent suppression of protons not coupled to C-13, and are able to measure couplings from regions that are crowded in bot h the proton and carbon frequency ranges. The experiments are applied to determine the long-range (II)J(CH) couplings in the sucrose molecul e, including coupling across the glycosidic linkage. These pulse seque nces are shown to provide accurate and efficient measurements of coupl ing constants that would be difficult or time-consuming to measure by other techniques. (C) 1998 Academic Press.