Showing papers by "Gary E. Martin published in 2002"
TL;DR: In this paper, the isolation and identification of degradants of a sample of the complex indoloquinoline alkaloid, cryptospirolepine, was undertaken after prolonged storage in DMSO solution using a combination of cryogenic NMR probe technology and CASE (Computer-Assisted Structure Elucidation) programs.
47 citations
TL;DR: In this article, a modified IMPEACH-MBC pulse sequence was used in conjunction with an optimization range from 4 to 50 Hz to demonstrate the technique using a mixture of 2- and 3-fluoropyridine, which had 2J(N,F) and 3J(n,F)-long-range couplings of −52 and 3.6 Hz, respectively.
Abstract: The first demonstrated example of 19F–15N long-range heteronuclear shift correlation spectroscopy at natural abundance is reported. Because of the very large variation in the size of 2J(N,F) vs 3J(N,F) long-range heteronuclear couplings, the utilization of one of the new accordion-optimized long-range heteronuclear shift correlations experiments is essential if all possible correlations are to be observed in a single experiment. A modified IMPEACH-MBC pulse sequence was used in conjunction with an optimization range from 4 to 50 Hz to demonstrate the technique using a mixture of 2- and 3-fluoropyridine, which had 2J(N,F) and 3J(N,F) long-range couplings of −52 and 3.6 Hz, respectively. Because of the size of the 2J(N,F) long-range coupling constant, a J-modulation of the long-range correlation response is observed in the spectrum resulting in a ‘doublet’ in F1 due to amplitude modulation. The size of the ‘doublet’ is shown to be a function of the parameter selection (t1max,Tmax,Tmin and spectral width in F1). This behavior is similar to F1 ‘skew’ associated with long-range correlation responses in ACCORD-HMBC spectra which has been analyzed in detail previously. Copyright © 2002 John Wiley & Sons, Ltd.
8 citations