Premium
New strategy for RDC‐assisted diastereotopic proton assignment using a combination of J ‐scaled BIRD HSQC and J ‐scaled BIRD HMQC/HSQC
Author(s) -
Snider Jonathan D.,
TrochePesqueira Eduardo,
Woodruff Shan R.,
Gayathri Chakicherla,
Tsarevsky Nicolay V.,
Gil Roberto R.
Publication year - 2012
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.3895
Subject(s) - chemistry , heteronuclear single quantum coherence spectroscopy , methylene , proton , tensor (intrinsic definition) , stereochemistry , two dimensional nuclear magnetic resonance spectroscopy , computational chemistry , analytical chemistry (journal) , medicinal chemistry , organic chemistry , mathematics , pure mathematics , physics , quantum mechanics
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 1 D CH for methine groups, the sum of 1 D CHa + 1 D CHb for methylene groups and the average 1 D CH3 value for methyl groups. In turn, the small molecule alignment tensor is calculated using these D values without the a priori assignment of CH 2 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 © 2012 John Wiley & Sons, Ltd.