A Nitrile Glucoside and Biflavones from the Leaves of Campylospermum excavatum (Ochnaceae).

The study of the MeOH extract of the leaves of Campylospermum excavatum led to the isolation of a nitrile glucoside, named campyloside C (1) and an original derivative of ochnaflavone, 7-O-methylochnaflavone (2), along with three known biflavonoids, amentoflavone, sequoiaflavone, and sotetsuflavone (3 - 5). The linkage site of the sub-units of 2 was confirmed by chemical correlation, after semi-synthesis of a trimethoxylated derivative of ochnaflavone (2a). The structures of these compounds as well as their relative and absolute configurations were assigned by 1D- and 2D-NMR experiments, HR-ESI-MS and Electronic Circular Dichroism (ECD) calculations.

New flavonoids C-glycosides from Rhabdophyllum arnoldianum.

Two new flavone glycosides, 3″-O-acetyl-7-O-methylvitexin (1) and 6″-α-rhamnopyranosyl-7-O-methylvitexin (2), along with nine known compounds (3-11) were isolated from the leaves of Rhabdophyllum arnoldianum (Ochnaceae). The structures of the new compounds were established by detailed spectroscopic studies and mass spectrometry, while known compounds were characterised by direct comparison of their reported NMR data with those found in the literature. All these compounds were the first reported from Rhabdophyllum genus.

NASCA-HMBC, a new NMR methodology for the resolution of severely overlapping signals: application to the study of agathisflavone.

Introduction: Standard NMR 2D heteronuclear HMBC spectra have a low resolution in the indirect carbon dimension, making it very difficult to assign signals to individual carbons when their chemical shifts are < 0.3 ppm apart.

Objective: To establish spectral aliasing for HMBC experiments to improve the resolution in the carbon dimension without increasing the total experimental time and avoiding ambiguities in the observed chemical shifts.

Spectral aliasing: a super zoom for 2D-NMR spectra. Principles and applications.

The NMR methodology based on spectral aliasing developed at the University of Geneva is reviewed. Different approaches aimed at increasing the resolution in the indirect carbon dimension of 2D heteronuclear experiments are presented with their respective advantages. Applications to HSQC, HMBC and other 2D heteronuclear experiments to the study of natural products and synthesis intermediates are shown.