AI Article Synopsis
- n-ADEQUATE is an advanced NMR technique that helps determine the structures of small molecules by identifying long-range carbon-carbon (C─C) correlations, but care is needed to filter out one-bond correlations.
- The dual-optimized, inverted J 1,n-ADEQUATE variant enhances this technique by allowing broadband inversion of direct responses, simplifying the identification process of these correlations.
- A new refinement introduces real-time bilinear rotation decoupling to improve sensitivity and resolution, demonstrated through experiments on various model compounds.
Article Abstract
1,n-ADEQUATE is a powerful NMR technique for elucidating the structure of proton-deficient small molecules that can help establish the carbon skeleton of a given molecule by providing long-range three-bond C─ C correlations. Care must be taken when using the experiment to identify the simultaneous presence of one-bond C─ C correlations that are not filtered out, unlike the HMBC experiment that has a low-pass J-filter to filter J responses out. Dual-optimized, inverted J 1,n-ADEQUATE is an improved variant of the experiment that affords broadband inversion of direct responses, obviating the need to take additional steps to identify these correlations. Even though ADEQUATE experiments can now be acquired in a reasonable amount of experimental time if a cryogenic probe is available, low sensitivity is still the main impediment limiting the application of this elegant experiment. Here, we wish to report a further refinement that incorporates real-time bilinear rotation decoupling-based homodecoupling methodology into the dual-optimized, inverted J 1,n-ADEQUATE pulse sequence. Improved sensitivity and resolution are achieved by collapsing homonuclear proton-proton couplings from the observed multiplets for most spin systems. The application of the method is illustrated with several model compounds.
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Article Synopsis
- n-ADEQUATE is an advanced NMR technique that helps determine the structures of small molecules by identifying long-range carbon-carbon (C─C) correlations, but care is needed to filter out one-bond correlations.
- The dual-optimized, inverted J 1,n-ADEQUATE variant enhances this technique by allowing broadband inversion of direct responses, simplifying the identification process of these correlations.
- A new refinement introduces real-time bilinear rotation decoupling to improve sensitivity and resolution, demonstrated through experiments on various model compounds.
Broadband inversion of 1J(CC) responses in 1,n-ADEQUATE spectra.
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November 2013
Merck Research Laboratories, Discovery and Preclinical Sciences, Process and Analytical Chemistry, Structure Elucidation Group, Rahway, NJ 07065, USA. Electronic address:
Establishing the carbon skeleton of a molecule greatly facilitates the process of structure elucidation, both manual and computer-assisted. Recent advances in the family of ADEQUATE experiments demonstrated their potential in this regard. 1,1-ADEQUATE, which provides direct (13)C-(13)C correlation via (1)J(CC), and 1,n-ADEQUATE, which typically yields (3)J(CC) and (1)J(CC) correlations, are more sensitive and more widely applicable experiments than INADEQUATE and PANACEA.
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