Synthesis of a mannose heptasaccharide existing in baker's yeast, Saccharomyces cerevisiae X2180-1A wild-type strain

Toward automated oligosaccharide synthesis

Carbohydrates have been shown to play important roles in biological processes. The pace of development in carbohydrate research is, however, relatively slow due to the problems associated with the complexity of carbohydrate structures and the lack of general synthetic methods and tools available for the study of this class of biomolecules. Recent advances in synthesis have demonstrated that many of these problems can be circumvented. In this Review, we describe the methods developed to tackle the problems of carbohydrate-mediated biological processes, with particular focus on the issue related to the development of the automated synthesis of oligosaccharides. Further applications of carbohydrate microarrays and vaccines to human diseases are also highlighted.

Allyl deprotection of galacturonic acid derivatives: mechanistic aspects of mercuric-catalyzed prop-1-enyl acetal cleavage

Different deallylation methods were assayed for selective deprotection of allyl galactopyranosiduronic acid derivatives. A two-step procedure using DABCO and (Ph(3)P)(3)RhCl followed by mercuric-assisted cleavage gave quantitative yields. Reaction in the presence of [(18)O]water allowed us to obtain evidence about the mechanism of prop-1-enyl cleavage.

[Synthesis of oligosaccharide fragments of mannan from Candida albicans cell wall and their BSA conjugates]

3-Aminopropyl glycosides of alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyra-nosyl-(1-->2)-alpha-D-mannopyranose, alpha-D-mannopyranosyl-(1-->3)-alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyranosyl-(l -- 2)-alpha-D-mannopyranose, and alpha-D-mannopyranosyl-(1-->2)-[alpha-D-mannopyranosyl-(1-->3)]-alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyranose were efficiently synthesized starting from ethyl 2-O-acetyl(benzoyl)-3,4,6-tri-O-benzyl-l-thio-alpha-D-mannopyranoside, ethyl 4,6-di-O-benzyl-2-O-benzoyl-1-thio-alpha-D-mannopyranoside, ethyl 4,6-di-O-benzyl-2,3-di-O-benzoyl-l-thio-alpha-D-mannopyranoside, and 2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranosyl bromide. The oligosaccharide chains synthesized correspond to the three structural types of side chains of mannan from Candida albicans cell wall. A conjugate of the third pentasaccharide with bovine serum albumin was prepared using the squarate method.

Syntheses of oligomannosides in solution and on a soluble polymer support: a comparison

The alpha-(1-->6)-linked and the alpha-(1-->2)-linked linear mannotetraose glycosides and, respectively, and the branched mannopentaoside [R=CH2(CH2)2CH2Cl] were synthesised by conventional methods in solution, using trichloroacetimidate donors, and the products were obtained in 39%, 42% and 40% overall yield, respectively. For comparative purposes, the same two linear tetrasaccharides were prepared by use of MPEG as a soluble polymer support, the yields being 34% and 14%, respectively. An attempted MPEG-supported synthesis of the branched pentasaccharide was unsuccessful. The merits and shortcomings of oligosaccharide syntheses on MPEG are discussed.

Facile syntheses of the hexasaccharide repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar A

Two hexasaccharides, beta-D-Xylp-(1-->2)-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)-]alpha-D-Manp-(1-->3)-[beta-D-GlcpA-(1-->2)-]alpha-D-Manp and beta-D-GlcpA-(1-->2)-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)-]alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)-]alpha-D-Manp, the repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar A, were synthesized as their methyl glycosides in a regio- and stereoselective manner.