Repetitive solid phase glycosylation on an alkyl thiol polymer leading to sugar oligomers containing 1,2-trans- and 1,2-cis-glycosidic linkages

Repetitive solid phase glycosylation with sugar trichloroacetimidates is performed on an alkyl thiol polymer, demonstrating the selective formation of glycosidic bonds. The alpha-mannose and alpha-fucose linkages representing examples of 1,2-trans- and 1,2-cis-glycosides are synthesized. It is shown that the presented system can be operated in a cyclic manner, thus allowing many consecutive reaction steps to be performed on the solid support. Reaction conditions for solid phase glycosylation and deprotection are described. Analysis of all solid phase reactions is performed by MALDI-TOF mass spectrometry; the yield of solid phase glycosylation is quantitative up to the tetrameric stage judged from the mass spectra obtained from partial product cleavage after each reaction. Cleavage conditions for analysis and preparative isolation by thiophilic Lewis acids and oxidative methods are optimized.