open access

https://hdl.handle.net/2115/8469

Application of 1D BIRD or X-filtered DEPT long-range C-C relay for detection of proton and carbon via four bonds and measuring long-range C-13-C-13 coupling constants

英語

long-range C-13-C-13 coupling constants

2006-01-05

John Wiley & Sons

Magnetic Resonance in Chemistry

44(4)

475-480

We propose the C-13-detecting 1D DEPT long-range C-C relay to detect super long-range H-C connectivity via four bonds (H-1-C-13-X-X-C-13, X represents C-12 or heteronuclear). It is derived from the DEPT C-C relay which detects the H-C correlations via two bonds (H-1-C-13-C-13) by setting the delays for J(CC) in the C-C relay sequence to the (LR)J(CC). This sequence gives correlation signals split by small (LR)J(CC), which seriously suffers from residual center signal. The unwanted signal is due to long-range C-H couplings ((LR)J(CH)). The expected relayed magnetization transfer (1)J(CH) -> (LR)J(CC) occurs in the H-1-C-13-X-(X)-C-13 isotopomer, whereas the unwanted signal of (LR)J(CH) comes from H-1-C-12-(X)-C-13 isotopomers, whose population is 100 times larger than that of the H-1-C-13-X-(X)-C-13 isotopomer. The large dispersive line of this unwanted center signal would be a fatal problem in the case of detecting small (LR)J(CC) couplings. This central signal could be removed by an insertion of BIRD pulse or X-filter. DEPT spectrum editing solved a signal overlapping problem and enabled accurate determination of particular (LR)J(CC) values. We demonstrate here the examples of structure determination using connectivity between H-1 and C-13 via four bonds, and the application of long-range C-C coupling constants to discrimination of stereochemical assignments.

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Accepted Manuscript

Copyright © 2006 John Wiley & Sons, Ltd.

0749-1581

0749-1581