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

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 (alpha, alpha') stereochemistry of trehalose.

Binding properties and esterase activity of monoclonal antibodies elicited against sucrose 6-heptylphosphonate.

Various sugar phosphonates were prepared by a Mitsunobu condensation between phosphonic diacids and properly protected carbohydrates. 6'-O-p-Aminophenylsucrose 6-heptylphosphonate was coupled to Bovine Serum Albumin (BSA) and Keyhole Limpet Hemocyanin (KLH) and the KLH conjugate was used for generation of monoclonal antibodies. Binding properties of these antibodies were screened by competitive enzyme-linked immunosorbent assay (ELISA) using the BSA conjugate. A monoclonal antibody with good binding properties showed a regioselective esterase activity toward 6-octanoylsucrose compared with 6'-octanoylsucrose.

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).