perfectBASH: Band‐selective homonuclear decoupling in peptides and peptidomimetics

Pure shift techniques have recently attracted much attention, as they have the ability to reduce spectral overlap and thus to simplify the analysis of complex and congested spectral regions. For peptides, band‐selective pure shift approaches are often the most reasonable choice among these, when spectra need to be simplified along proton dimensions. Band‐selective approaches usually offer the highest sensitivity of all pure shift methods, albeit at the cost that signals can only be acquired in a single‐frequency region of the spectrum, in which protons are well isolated in the proton spectrum. For α‐peptides, signals are usually acquired either in the amide‐proton region or in the α‐proton region. Herein, we present experiments, which enable the pure shift acquisition in both the amide‐proton and the α‐proton regions of α‐peptides simultaneously, without sacrificing the characteristics of band‐selective pure shift methods to provide high sensitivity. The "perfectBASH" approach discussed here combines the perfect echo experiment with band‐selective decoupling. It can be used for band‐selective pure shift acquisition of 1H, TOCSY, CLIPCOSY, relayed CLIP‐COSY, NOESY, and EASY‐ROESY spectra, with proton– proton decoupling over the full backbone region of α‐peptides, which is most interesting for samples prepared without isotopic enrichment. As the utility of this technique is by no means limited to α‐peptides, we further illustrate its utility for 1H‐NMR studies of a peptidomimetic oligourea.