期刊
MAGNETIC RESONANCE IN CHEMISTRY
卷 50, 期 -, 页码 S86-S91出版社
WILEY-BLACKWELL
DOI: 10.1002/mrc.3895
关键词
NMR; H-1; C-13; J-scaled HSQC; J-scaled HMQC/HSQC; residual dipolar couplings; PMMA gels; diastereotopic protons; strychnine
资金
- NSF [CHE-0130903, CHE-1039870, CHE-1111684, CHE-1111929]
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [1111684, 1111929] Funding Source: National Science Foundation
A new strategy to assign diastereotopic protons was developed on the basis of residual dipolar couplings (RDCs) collected in compressed poly(methyl methacrylate) (PMMA) gels. A combination of 2D J-scaled BIRD HSQC and J-scaled BIRD HMQC/HSQC NMR experiments was used to collect the RDC data. In the proposed strategy, the first experiment is used to measure D-1(CH) for methine groups, the sum of D-1(CHa) + D-1(CHb) for methylene groups and the average D-1(CH3) value for methyl groups. In turn, the small molecule alignment tensor is calculated using these D values without the a priori assignment of CH2 diastereotopic protons. The D values of each individual CH bond (CHa and CHb) of each methylene group in the molecule are then predicted using the calculated alignment tensor and these values compared with the results from the HMQC/HSQC experiment, leading to their unambiguous assignment. This strategy is demonstrated with the alkaloid strychnine that contains five methylene groups with diastereotopic protons, and our results fully agree with the previously reported assignment using combinations of permutated assignments. Copyright (C) 2012 John Wiley & Sons, Ltd.
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