Once a full dataset s (t 1, t 2, t 3) has been acquired, a pseudo-2D dataset is produced by stitching together chunks of s (t 3) of duration 1/sw2 for successive increments of t 2. The result is a pseudo-2D
dataset s(t1,t2′) in which signal evolves as normal (δ C only) as a function of t 1, and as a pure Dapagliflozin mw shift 1H signal in t2′ (δ H, 2J HH and 1J CH only). Typically sw2 is 40–100 Hz, and 16–32 FIDs s (t 3) are acquired, giving a maximum t2′ of 160–800 ms and yielding ample spectral resolution for coupling constant measurement. It is important to note that the best results require very careful timing of the BIRD(d) and 1H 180° pulse decoupling elements. Therefore, the correct setting of the delays in the sequences of Fig. 1, as detailed in the figure legend, is critical. As in the original CLIP-HSQC experiment [10], a
carbon 90° pulse is employed to purge the undesired residual dispersive antiphase proton magnetization prior to detection. In the case of the CLAP-HSQC sequence, proton magnetization is detected in antiphase, so only a Talazoparib manufacturer short spin-echo sequence to accommodate the coherence selection gradient pulse (G4) follows, and the purging carbon pulse is omitted here. The broadband proton-decoupled sequences of Fig. 1 have been tested on the small model compounds depicted in Scheme 1. First, to investigate the robustness and tolerance of the experiments with regard to mismatch of the BIRD/INEPT delays in the sequence, a 13C-labeled compound, [C-1]-methyl-α,β-d-glucopyranoside (1), was used. The results are shown in Fig. 2, which presents the C-1 doublets obtained with the broadband proton-decoupled CLAP-HSQC sequence using BIRD/INEPT delays adjusted to a range of nominal one-bond heteronuclear coupling constant spanning 100–180 Hz. It can clearly be seen that the intensities of the signals are, as expected, significantly degraded when the delays are mismatched to the coupling constant,
but that the pure absorptive quality of the lineshapes remains basically unaffected, allowing accurate measurement of couplings even in anisotropic Mephenoxalone samples where net coupling constants vary widely. These results clearly demonstrate that the proposed sequences, used in combination with the pulsed field gradient coherence selection scheme illustrated in Fig. 1, efficiently remove the undesired residual dispersive coherences arising from the mismatch between delays and 1JCH. Applications of the broadband proton-decoupled CLIP/CLAP-HSQC experiments of Fig. 1 under isotropic and partially orienting sample conditions are demonstrated using model compound 2 (Scheme 1). A comparison between CLIP- and CLAP-HSQC spectra acquired with the conventional sequence [10] and the broadband decoupled sequence of Fig. 1 is given in Fig. 3.