Synthesis of Trisaccharides and Tetrasaccharides by Means of Intramolecular Glycosylation Supported by Rigid Spacers

摘要: Treatment of α,α′-dibromo-m-xylylene with 6-O-unprotected thiomaltoside 4 as glycosyl donor ( 5), followed by 4-O-unprotected galactoside derivative 6 acceptor, afforded β-linked macrocyclic trisaccharide 9β in high yield after removal the 3-O-MPM protective group and subsequent intramolecular glycoside bond formation. Similarly, same sequence steps, corresponding tetrasaccharide 14β was obtained from 5 4b-O-unprotected lactoside 11. For reiterative formation, treatment 3-O-unprotected thioglycoside 15 16), 4,6-O-unprotected glucoside, glycosylation maltotrioside 22, which transformed into known 23. A slight modification protecting-group pattern synthesis resulted generally higher yields ligation building blocks to m-xylylene spacer, particularly second step, thus providing 40α, maltotriosides 41α 41β.