Preparation of both enantiomers of a synthon for novel nucleoside analogs by enzymatic desymmetrization of a meso-diol with a methylene cyclopropane skeleton

International audienceThe enzymatic desymmetrization of methylenecyclopropane diol or its corresponding diacetate derivative, generated from a [2+1] cycloaddition between dioxepin and methylchlorocarbene, is described. After screening five commercial lipases, the two enantiomers of acetic acid 2-hydroxymethyl-3-methylene-cyclopropylmethyl ester are obtained in high yields and excellent enantioselectivities by using PFL or LPP in organic solvent. The stereostructure of the desymmetrization products was established by X-ray analysis. We also reported a new example with this non racemic chiral building block where the sign of optical rotation is dramatically solvent dependent and inverted. Using these enantiopure building blocks, a synthesis of novel nucleoside analogs is also presented. (C) 2011 Elsevier Ltd. All rights reserved

Phytochemical study of Croton mayumbensis J. Léonard (Euphorbiaceae)

International audienc

Antiplasmodial activity of extracts and compounds from Vitex madiensis Oliv. (Lamiaceae)

National audienc

In vitro antiplasmodial activity and cytotoxicity of extracts and fractions of Vitex madiensis, medicinal plant of Gabon.

International audienceVitex madiensis Oliv. (Lamiaceae) is traditionally used to treat malaria symptoms in Haut-Ogooué, Gabon. Leaves and stem barks extracts were obtained using dichloromethane (CH(2)Cl(2)), ethyl acetate (EtOAc) and methanol (MeOH) as extraction solvents and fractionated on silica gel column. The in vitro antiplasmodial activity of CH(2)Cl(2), EtOAc and MeOH extracts and fractions was evaluated against the chloroquine-resistant FCB strain and field isolates of Plasmodium falciparum using the DELI test. The cytotoxicity of the extracts was tested on MRC-5 and THP1 cells using the tetrazolium salt MTT colorimetric assay, and the selectivity index (SI) of each extract was calculated. CH(2)Cl(2) extract, the EA1 fraction from EtOAc extract of stem barks and cyclohexane (L(cycl)), dichloromethane (L(DM)) and butanol (L(but)) fractions from MeOH/H(2)O extract of leaves exhibited the highest in vitro antiplasmodial activity on FCB strain and field isolates (IC(50) from 0.53 to 4.87 μg/ml) with high selectivity index (of 20.15-1800). These data support the use of V. madiensis in malaria treatment along with continued investigations within traditional medicines in the search of new antimalarial agents. The EA1, C(6)H(12) and CH(2)Cl(2) fractions could be selected for future investigation or/and for the treatment of malaria symptoms after standardization