Straightforward measurement of individual 1J(CH) and 2J(HH) in diastereotopic CH2 groups

The C-HA cross-peak corresponding to a diastereotopic CH AHB methylene spin system exhibits a characteristic 1:0:1 multiplet pattern along the indirect dimension of a ω1-coupled HSQC spectrum. It is shown here that the use of the initial 13C Boltzmann polarization instead of the regular INEPT-based 1H Boltzmann polarization makes visible the central lines of this multiplet pattern. A spin-state-selective method is proposed for the efficient measurement of both 1J(CHA) and 1J(CHB) along the indirect dimension of a 2D spectrum as well as to the magnitude and the sign of the geminal 2J(HAHB) coupling constant from the straightforward analysis of a single four-component E.COSY cross-peak. Additionally, the extraction of 1J(CH) values for CH and CH 3 multiplicities can be also performed from the same spectrum. The success of the method is also illustrated for the determination of residual dipolar 1D(CH) and 2D(HH) coupling constants in a small molecule weakly aligned in a PMMA swollen gel. © 2014 Elsevier Inc. All rights reserved.