Richard Plantier-Royon

Development of Agriculture Left-Overs: Fine Organic Chemicals from Wheat Hemicellulose-Derived Pentoses

This review is dedicated to wheat hemicelluloses and its main components D-xylose and L-arabinose as raw materials for fine organic chemistry. The context of the wheat agro-industry, its by-products, and extraction and hydrolysis of hemicelluloses to produce the pentoses are considered. The straightforward preparation of pentose-based surfactants, their properties, and their situation in the field of carbohydrate-based surfactants are addressed. Multistep transformations of pentoses are also described, first from a methodology point of view, with the aim of producing multifunctional enantiopure building-blocks, then considering targeted natural and/or bioactive products. Selected reactions of furfural, an important dehydration product of pentoses, are also presented.

C-Difluoromethylene-containing, C-trifluoromethyl and C-perfluoroalkyl carbohydrates. Synthesis by carbohydrate transformation or building block methods

The synthetic methods for preparing carbohydrates bearing a C-branched substituent of the type CF2-Y, with Y = F, Y = CnF(2n + 1) or Y = a carbon-attached or heteroatom-attached nonfluorinated residues, are reviewed. Both direct introduction of C-branched fluorinated substituents (direct trifluoromethylation, perfluoroalkylation or difluoromethylenation) and building block methods from fluorinated synthons are considered.

Enzymatic synthesis of alkyl arabinofuranosides using a thermostable α-l-arabinofuranosidase

Abstract A thermostable α- l -arabinofuranosidase was tested for its ability to perform transglycosylation with different alcohol acceptors. Reactions were characterized by high rates with optimal synthesis being obtained within 10 min. Both primary and secondary alcohols could act as acceptors in transarabinosylation but yields of alkyl arabinosides decreased with increasing alkyl chain length.

Reactions of difluoroenoxysilanes with glycosyl donors: synthesis of difluoro-C-glycosides and difluoro-C-disaccharides.

Difluoroenoxysilanes, prepared from acylsilanes and trifluoromethyltrimethylsilane under fluoride activation, were glycosylated with some glycosyl donors (acylglycosides, glycals) to yield difluoro-C-glycosides with a difluoromethylene group in the place of the anomeric oxygen. This reaction strongly depends on the substituent in the 2-position of the glycosyl donor. Application of this methodology to a xylose-derived acylsilane led to the formation of difluoro-C-disaccharides as an isosteric O-glycosyl mimetic.

Enzymatic synthesis of alkyl β-D-xylosides and oligoxylosides from xylans and from hydrothermally pretreated wheat bran

Direct and efficient preparation of pentyl and octyl β-D-xylosides and oligoxylosides has been achieved from xylans and n-pentanol or n-octanol in aqueous medium with xylanases. The method has been successfully applied with xylooligosaccharides produced from hydrothermally pretreated wheat bran to produce octyl oligoxylosides. The pentose-based surfactants thus obtained exhibit good surface properties compared to other alkyl glycosides. These molecules represent interesting candidates for the production of new green surfactants.

STEREOSELECTIVITY OF THE NUCLEOPHILIC F-ALKYLATION OF CARBONYLATED CARBOHYDRATES

Abstract The addition of F-alkyl organometallics to carbonylated carbohydrates 1 – 3 was carried out using trimethylsilyl or bromomagnesium reagents. The results are strongly dependent upon both the nature of the metal and of the substrate. Compounds 1 and 2 were transformed with high stereoselectivity into the l -ido adduct using F-organomagnesium reagents, whereas the d -allo adduct was obtained with complete stereoselectivity using fluoride activated addition of F-organosilanes on compound 3 . Comparison with literature data emphasizes the enhanced stereoselectivity exhibited by perfluoroorganometallic reagents. The difference between the stereoselectivity of the addition of magnesium versus silyl reagents was attributed to chelation effects.

Mixed organofluorine - organosilicon chemistry. 6. Synthesis of gem-difluoro-C-glycosides and C-disaccharides from acylsilanes and trifluoromethyltrimethylsilane. An exploratory study

Abstract Difluoroenoxysilanes, prepared from acylsilanes and trifluoromethyltrimethylsilane under fluoride activation, were glycosylated by glucal to yield C -difluoroglycosides with a difluoromethylene group in place of the anomeric oxygen. Application of this methodology to a xylose-derived acylsilane led to a C -difluorodisaccharide.

Fluorophosphonylated Nucleoside Derivatives as New Series of Thymidine Phosphorylase Multisubstrate Inhibitors

The synthesis of new class of potential TPase inhibitors containing a difluoromethylphosphonate function as phosphate mimic is reported. This new series was prepared from a readily available fluorinated building block in few steps. Two series were evaluated as potential inhibitors: a linear series and a conformational constrained series. The activity of these multisubstrate inhibitors depends on the size of the spacer introduced between the pyrimidine ring and the phosphonate function. Best results were observed from triazolyl derivatives, easily obtained from propargylthymine and corresponding azides.

Dienophilic reactivity of perfluoroalkenyl ketones in Diels–Alder reactions

Abstract Perfluoroalkenyl ketones, obtained by reaction of perfluoroorganometallic reagents with acylsilanes, are shown to be versatile dienophiles in Diels–Alder reactions with various dienes.

The spirocyclopropyl moiety as a methyl surrogate in the structure of L-fucosidase and L-rhamnosidase inhibitors

Nitrogen-in-the-ring analogues of l-fucose and l-rhamnose were prepared, which feature a spirocyclopropyl moiety in place of the methyl group of the natural sugar. The synthetic route involved a titanium-mediated aminocyclopropanation of a glycononitrile as the key step. Four new spirocyclopropyl iminosugar analogues were generated, which displayed some activity towards l-fucosidase and l-rhamnosidase.