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International audience; Alkylglycerols (AKGs) with a straight-chain alkane or alkene are ether lipids abundant in the liver oil of some elasmobranch fish species such as ratfishes and some sharks. Natural shark liver oil (SLO) mixture displays several known biological activities and most of its identified alkylglycerols were also obtained individually in pure form by total synthesis. However, the synthesis of alkylglycerols containing at least one alkyne moiety in the alkyl chain has yet not been reported. In this work, we describe the first total synthesis of 1-O-alkylglycerols based alkyne (2S)-3-((4-methoxytridec-6-yn-1-yl)oxy)propane-1,2-diol (10) and (S)-3-(((R)-12-methoxyoctadec-9-yn-1-yl)oxy)propane-1,2-diol (11), analogues of bioactive ether lipids found in the SLO mixture. Oxiranes opening by alkynyl boranes and solketal etherification are the key steps with a global yield up to 72 % in eight steps sequence.

The low resolution of standard 2D HMBC spectra makes it very difficult to assign signals of close pairs of carbons. The NASCA-HMBC (Non-ambiguous Assignment by Superposition of Coupled Aliased HMBC) combines a pair of aliased HMBC spectra to provide one order of magnitude increase in the resolution. Application to agathisflavone, a biflavonoid found in Ouratea gilgiana resulted in spectra with a sufficiently high resolution to make the assignment straightforward and report, for the first time, its full assignment.

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 structure of these compounds as well as their relative and absolute configurations were assigned by 1D and 2D NMR experiments, HRESIMS and Electronic Circular Dichroism (ECD) calculations. A low-pass J filter HMBC experiment was performed in order to define the stereochemistry of the double bond of 1. All of the biflavonoids were evaluated against protozoan parasites. Amentoflavone moderately inhibited the promastigote form of Leishmania infantum. This article is protected by copyright. All rights reserved.

International audience; Two new flavone glycosides, 3 ''-O-acetyl-7-O-methylvitexin (1) and 6 ''-alpha-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. The biological assays on crude extracts and compounds of this plant demonstrated that the crude extracts possess significant antimicrobial activity against Gram-positive bacteria.

A new indole alkaloid, calanthumindole (4), and three known biflavonoids, amentoflavone, sequoiaflavone, and podoscarpusflavone B, were isolated from Campylospermum calanthum (Ochnaceae). Calanthumindole is a new indole alkaloid of the serotobenine family characterized by the presence of a C[DOUBLE BOND]C bond between atoms C(7′) and C(8′) of the furan ring. This is the first compound to have a fully unsaturated furan ring among the members of this family. The combination of NMR and DFT allowed the determination and comparison of the 3D structures and relevant conformational characteristics of serotobenine (1), flavumindole (2), and calanthumindole (4).

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. METHODOLOGY The NASCA HMBC (Non ambiguous Assignment by Superposition of Coupled Aliased HMBC) methodology combines a pair of HMBC spectra recorded with slightly different carbon windows to provide typically one order of magnitude increase in the resolution and unambiguous chemical shifts. RESULTS The application of this methodology to a biflavonoid found in Ouratea gilgiana resulted in spectra with a sufficiently high resolution to make the assignment straightforward and report for the first time the full assignment of agathisflavone. CONCLUSION The methodology should find many applications in dimeric and oligomeric compounds such as peptides carbohydrates polyketides and other cases where signal clustering is expected.

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. HSQC-based experiments for diffusion measurements, kinetics studies and titrations experiments all take advantage of spectral aliasing to reduce the experimental time from unrealistically long acquisition times to overnight experiments. The roles of computational methods such as DFT/GIAO and Logic for Structure Determination (LSD) in structure determination are discussed.