Discovery of compounds blocking the proliferation of Toxoplasma gondii and Plasmodium falciparum in a chemical space based on piperidinyl-benzimidazolone analogs.

A piperidinyl-benzimidazolone scaffold has been found in the structure of different inhibitors of membrane glycerolipid metabolism, acting on enzymes manipulating diacylglycerol and phosphatidic acid. Screening a focus library of piperidinyl-benzimidazolone analogs might therefore identify compounds acting against infectious parasites. We first evaluated the in vitro effects of (S)-2-(dibenzylamino)-3-phenylpropyl 4-(1,2-dihydro-2-oxobenzo[d]imidazol-3-yl)piperidine-1-carboxylate (compound 1) on Toxoplasma gondii and Plasmodium falciparum. In T. gondii, motility and apical complex integrity appeared to be unaffected, whereas cell division was inhibited at compound 1 concentrations in the micromolar range. In P. falciparum, the proliferation of erythrocytic stages was inhibited, without any delayed death phenotype. We then explored a library of 250 analogs in two steps. We selected 114 compounds with a 50% inhibitory concentration (IC50) cutoff of 2 µM for at least one species and determined in vitro selectivity indexes (SI) based on toxicity against K-562 human cells. We identified compounds with high gains in the IC50 (in the 100 nM range) and SI (up to 1,000 to 2,000) values. Isobole analyses of two of the most active compounds against P. falciparum indicated that their interactions with artemisinin were additive. Here, we propose the use of structure-activity relationship (SAR) models, which will be useful for designing probes to identify the target compound(s) and optimizations for monotherapy or combined-therapy strategies.

Chemical inhibitors of monogalactosyldiacylglycerol synthases in Arabidopsis thaliana.

Monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) are the main lipids in photosynthetic membranes in plant cells. They are synthesized in the envelope surrounding plastids by MGD and DGD galactosyltransferases. These galactolipids are critical for the biogenesis of photosynthetic membranes, and they act as a source of polyunsaturated fatty acids for the whole cell and as phospholipid surrogates in phosphate shortage. Based on a high-throughput chemical screen, we have characterized a new compound, galvestine-1, that inhibits MGDs in vitro by competing with diacylglycerol binding. Consistent effects of galvestine-1 on Arabidopsis thaliana include root uptake, circulation in the xylem and mesophyll, inhibition of MGDs in vivo causing a reduction of MGDG content and impairment of chloroplast development. The effects on pollen germination shed light on the contribution of galactolipids to pollen-tube elongation. The whole-genome transcriptional response of Arabidopsis points to the potential benefits of galvestine-1 as a unique tool to study lipid homeostasis in plants.

(E)-alpha-substituted gamma-alkoxyallylboronic esters as new reagents: synthesis and reactivity toward aldehydes.

We have developed a synthesis of new allylboration reagents based on an allylic rearrangement. This approach led to the alpha-substituted gamma-alkoxyallylboronates 2 with a high stereoselectivity in favor of the E-isomer, independent of the organometallic used. We have also studied the reactivity of these reagents toward aldehydes, showing that the allylboration reaction occurs with an excellent diastereoselectivity to give the anti-diol derivatives 5. Moreover, the sequence can be carried out in a "one-pot" procedure avoiding the purification of allylboronates.

Catalytic enantioselective three-component hetero-[4+2] cycloaddition/allylboration approach to alpha-hydroxyalkyl pyrans: scope, limitations, and mechanistic proposal.

This article describes the design and optimization of a catalytic enantioselective three-component hetero-[4+2] cycloaddition/allylboration reaction between 3-boronoacrolein, enol ethers, and aldehydes to afford alpha-hydroxyalkyl dihydropyrans. The key substrate, 3-boronoacrolein pinacolate (2) was found to be an exceptionally reactive heterodiene in the hetero-[4+2] cycloaddition catalyzed by Jacobsen's chiral Cr(III) catalyst 1. The scope and limitations of this process were thoroughly examined. The adduct of 3-boronoacrolein pinacolate and ethyl vinyl ether was obtained in high yield and with over 95 % enantioselectivity. This cyclic alpha-chiral allylboronate adds to a very wide variety of aldehyde substrates, including unsaturated aldehydes and alpha-chiral aldehydes to give diastereomerically pure products. Acyclic 2-substituted enol ethers can be employed, in which case the catalyst promotes a kinetically selective reaction that favors Z enol ethers over the E isomers. Surprisingly, 3-boronoacrolein pinacolate was found to be a superior heterodiene than ethyl (E)-4-oxobutenoate, and a mechanistic interpretation based on a possible [5+2] transition state is proposed.

A novel diastereoselective route to alpha-hydroxyalkyl dihydropyrans using a hetero Diels-Alder/allylboration sequence.

The development of a new strategy for the synthesis of alpha-hydroxyalkyl dihydropyrans is reported. This approach is based on a tandem hetero[4+2]/allylboration reaction.

A novel diastereoselective route to alpha-hydroxyalkyl dihydropyrans using an hetero Diels-Alder/allylboration sequence.

The development of a new strategy for the synthesis of alpha-hydroxyalkyl dihydropyrans is reported. This approach is based on a tandem hetero[4 + 2]/allylboration reaction.