NMR Spectroscopy: Increased Sensitivity for Detecting Heteronuclear ¹H-¹³C Couplings through Multiple and Single Bonds

Abstract

A new 20 pulse sequence HMSC (Heteronuclear Multiple- and Single-bond coupling Correlations) for the simultaneous detection of long-range and one-bond heteronuclear connectivities is proposed, which allows the two types of responses to be separated and the corresponding ⁿJ_CH and ¹J_CH connectivity maps to be calculated. Unlike standard methods, designed to measure one single type of heteronuclear spin-spin interaction, and to efficiently suppress the other, both ⁿJ_CH and ¹J_CH are measured simultaneously in a single experiment with the HMSC pulse sequence. Compared to the common strategy with two standard experiments applied one after the other, e.g. HMBC and HMQC, valuable measuring time may be saved with this single experiment approach. The efficiency of the new pulse sequence and the quality of the corresponding spectra is demonstrated and compared with the results obtained with the standard HMBC experiment using bacdanol.
The attractive and unique single experiment approach together with its easy experimental set-up and straightforward data processing makes HMSC a valuable experimental alternative for the today's more time-consuming 'two-step' practice and makes it suitable for standard routine applications.