Marie-Christine Scherrmann

Chemical Synthesis of Linear and Cyclic Unnatural Oligosaccharides by Iterative Glycosidation of Ketoses

The development of an efficient method for the stereoselective synthesis of alpha-D-(2-->1)-linked ketoside oligomers is described. The method is based on an iterative protocol composed of two key steps: a) the coupling of a thiazolylketosyl phosphite donor with an hydroxymethylketoside acceptor; and b) the introduction of the hydroxy-methyl group at the anomeric carbon atom of the resulting oligomer. To highlight its efficiency, the protocol was used in the assembly of D-galacto-2-heptulopyranose-containing oligoketosides through alpha-(2-->1) linkages up to the pentameric stage. The yield of the isolated oligomers ranged from 48 % in the first cycle to 29% in the fourth cycle. Having employed a pentenyl-substituted hydroxymethylketoside acceptor in the first cycle, all the derived oligomers contained the pentenyl group at their reducing end. This group was exploited to transform the linear oligomers into cyclic products through intramolecular glycosidation. The major product derived from the linear trisaccharide was confirmed by X-ray crystallography to be the cyclotris-(2-->1)-(alpha-D-galacto-2-heptulopyranosyl). The structure of this compound was essentially that of a [9]crown-3 ether bearing three galactopyranose rings spiroanellated in a propellerlike fashion. This arrangement of carbohydrate units linked to the crown ether created a densely alkoxylated cavity suitable for the encapsulation of alkali-metal cations (Li, Na, K, Ca, Mg).

Furan-based synthesis of C-glycosyl carboxylates

Abstract The installation of the 2-furyl ring at the anomeric carbon of 2,3,4,6-tetra-O-benzyl- D -glucopyranose and 2,3:5,6-di-O-isopropylidene- D -mannofuranose is carried out either by addition of 2-lithiofuran to the correspondinglactones either by direct C-glycosidation of the O-acetyl derivatives with furan; the resultant 2-furyl C-glycosides are converted to carboxylic acids by the oxidative cleavage of the furan nucleous.

Investigation of the aqueous transmetalation of π-allylpalladium with indium salt: the use of the Pd(OAc)2–TPPTS catalyst

pi-Allylpalladium complexes could be generated in water by the palladium(0) water soluble catalyst prepared in situ from palladium acetate and TPPTS. These complexes were transmetalated with indium to react with benzaldehyde. The aqueous solution of Pd(0)(TPPTS)(n) could be reused without deterioration of the catalyst in the first and second recycling. The system proved to be efficient with primary and secondary allylic substrates. The stereochemical outcome of the allylation through umpolung of allylpalladium, was also studied using models with a restraint conformation.

Determination of the global material economy (GME) of synthesis sequences—a green chemistry metric to evaluate the greenness of products

Evaluating the greenness of a product is a social, economical and scientific challenge in chemistry. Green metrics in terms of mass can be determined from the characteristics of all the reactions involved in the total synthesis of the product. In this work we propose a new paradigm to determine the global material economy of the whole sequence. We have demonstrated that this key metric is directly proportional to the global atom economy of the corresponding total synthesis. The mathematical algorithm to calculate the global material economy can be applied to any process, whatever the number of the points of convergence in the synthesis, allowing the determination, in terms of mass, of the greenness of a product with respect to all the starting materials involved in the total synthesis.

New access to C-disaccharide analogs of α, α-trehalose using an aqueous hetero Diels-Alder reaction

Abstract C -disaccharide analogs of trehalose were prepared using an aqueous Diels-Alder reaction as a key step. The resulting major stereoisomer was shown by NMR spectroscopy analysis to have the correct (α, α′) stereochemistry of trehalose.

Synthesis of C‐3 Branched Allyl and Pentadienyl Glucosamines via Radical Coupling of Sugar‐Thionocarbonates

Abstract The intermolecular AIBN‐promoted free radical reaction of glucosamine thionocarbonates as radical donors, and allyl or pentadienyl‐tributyltin reagents gave the expected C‐3 branched sugar derivatives in good yield and with total equatorial selectivity.

Chapter 9:Electrochemical glycosylation

During the last three decades, electrochemical glycosylation performed by anodic oxidation of O-, S-, Se-, and Te-glycosides or by cathodic reduction of glycosyl halides has allowed the synthesis of a large number of complex O-, N-, and C-glycosyl derivatives.