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The conformational behavior of two C-glycosyl analogues of the sialyl-Tn antigen has been determined by a combination of NMR methods and molecular mechanics calculations. Both compounds show a major solution conformation that is drastically different from the major one of the natural compound.

Glycoaminoxy acids, a new class of sugar building blocks bearing both aminoxy and carboxylic acid functional groups on the sugar ring, have been efficiently synthesized from α-C-allyl glycosides. These compounds can be easily used for the synthesis of an N-oxy-amide-linked disaccharide and glycosyl amino acid mimetics.

Treatment of the anomeric 2-thiopyridyl derivative of N-acetylneuraminic acid (sialic acid or Neu5Ac) with samarium diiodide in the presence of aldehydes or ketones provides the corresponding C-sialylated derivatives in excellent yields. The efficiency of the reductive samariation of the anomeric 2-pyridylsulfide moiety in the Neu5Ac series does not require any cosolvent or additive. This samarium Reformatsky-like reaction from anomeric 2-pyridylsulfide derivatives of Neu5Ac provides an efficient and highly stereoselective access to a-2,6-C-disaccharides.

The reductive metallation of the readily available peracetylated derivatives of methyl N-acetylneuraminate 3a and 3b by samarium diiodide without any additive generates the corresponding anomeric samarium(III) organometallics. These intermediates react efficiently with carbonyl compounds under Barbier conditions, providing a fast synthesis of C-ketosides. The α- and β-acetates are equally effective, and excellent yields are obtained for coupling with cyclic ketones. The procedure has been conveniently applied to the synthesis of a C-ketoside of N-acetylneuraminic acid with an attached linker, ready to use as a building block in the elaboration of multivalent biological probes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Treatment of the anomeric 2-thiopyridyl derivative of N-acetylneuraminic acid (sialic acid or Neu5Ac) with samarium diiodide in the presence of aldehydes or ketones provides the corresponding C-sialylated derivatives in excellent yields. The efficiency of the reductive samariation of the anomeric 2-pyridylsulfide moiety in the Neu5Ac series does not require any cosolvent or additive. This samarium Reformatsky-like reaction from anomeric 2-pyridylsulfide derivatives of Neu5Ac provides an efficient and highly stereoselective access to a-2,6-C-disaccharides.