Measurement of long‐range proton–carbon coupling constants from pure in‐phase 1D multiplets

Abstract

The SELective INverse detection of carbon-proton CORrelation pulse sequence that yields a 1D spectrum of a proton directly bonded to a selected carbon resonance has been converted into a proton and carbon double-selective variant that provides a (1)H spectrum of a selected proton that is long-range coupled to a specific carbon resonance. The resulting 1D proton multiplet exhibits a pure absorptive in-phase lineshape for precise measurement of specific long-range proton-carbon coupling constants in small organic molecules at natural abundance.

A Method for the Rapid and Simple Measurement of the Magnitude and Relative Sign of 1H–19F Coupling Constants

“…[10] Thus, doubly-selective 1D HSQC experiments with inter-pulse delays optimized to long-range 1 H-13 C coupling (hereafter denoted as 1D LR-HSQC for clarity) were carried out to determine the 1 H-19 F coupling constants for protons separated by more than one bond from C2Ј. A recently developed 1D HSQC variant that includes proton and carbon Gaussian-shaped pulses was used to select the protons showing long-range coupling to C2Ј.…”

LR‐selHSQMBC: Simultaneous Detection and Quantification of Very Weak Long‐Range Heteronuclear NMR Correlations

“…The advantages of using a 1 H frequency‐selective version of the HSQMBC experiment (selHSQMBC) that has been previously reported to measure n J CH coupling constants from pure absorption IP coupling J patterns is analyzed herein . We want to explore experimental solutions in which only the intensity modulation of n J CH exclusively survives, while at the same time unwanted AP contributions due to both n J CH and J HH phase modulations are efficiently suppressed.…”

“…[9] On the other hand, HSQMBC-TOCSY [10] and ADEQUATE experiments [11][12] are alternative NMR tools to detect such longer-range correlations, although the limitations in sensitivity due to additional relaxation effects or the required 13 C-13 C selection at natural abundance are challenges to overcome.The advantages of using a 1 H frequency-selective version of the HSQMBC experiment (selHSQMBC) that has been previously reported to measure n J CH coupling constants from pure absorption IP coupling J patterns is analyzed herein. [13][14][15][16][17][18][19] We want to explore experimental solutions in which only the intensity modulation of n J CH exclusively survives, while at the same time unwanted AP contributions due to both n J CH and J HH phase modulations are efficiently suppressed. We intend to evaluate the performance of the selHSQMBC experiment for observing cross-peaks corresponding to very small n J CH coupling values, to measure them robustly, simultaneously determining their positive/negative sign.…”

Investigation of two‐ and three‐bond carbon–hydrogen coupling constants in cinnamic acid based compounds

“…The compounds were checked using routine analytical techniques to confirm the structure of the compounds. Each of the samples was subjected to complete NMR structure verification using 1 H, 13 C, COSY, HSQC and HMBC.…”

“…Other experiments like EXCIDE [7] , HSQC-HECADE [8] and J-HMBC [9] , in which the n J CH coupling evolves in the indirect dimension, have been successfully applied but require long experimental time to achieve the desired resolution. Recently, Parella et al [10][11][12][13][14][15] used selective HSQMBC experiments acquired in two different modes, inphase and antiphase (IPAP), to extract the n J CH coupling constants. The processing of the data involves two steps, in which the data are added (IP+AP) and subtracted (IPÀ AP), and the corresponding rows from these 2D datasets are compared to extract the n J CH .…”