Synthesis of linear β-(1→4)-galacto-hexa- and heptasaccharides and studies directed towards cyclogalactans
2002; Elsevier BV; Volume: 337; Issue: 21-23 Linguagem: Inglês
10.1016/s0008-6215(02)00081-2
ISSN1873-426X
AutoresMarkus Oberthür, Siegfried Peters, Saibal Kumar Das, Frieder W. Lichtenthaler,
Tópico(s)Polysaccharides and Plant Cell Walls
ResumoSynthesis of an exclusively β-(1→4)-linked galactohexa- and heptasaccharide is described by coupling a 2-O-pivaloyl-3,6-O-allyl-protected thiogalactobioside donor with an equally protected, yet terminally 4-OH-free galactopentaoside. The same approach though failed to elaborate cyclic oligomers, as neither cyclodimerization of the correspondingly protected thiogalactotriosides with a 4′′-OH could be effected, nor intramolecular glycosidation of the respective hexa- and heptagalactosides with an unprotected 4-OH at one, and phenylthio or sulfoxido groups at the reducing end. The causative factors underlying this are attributed to an inadequate predisposition of the linear β-(1→4)-galactan chains to adopt the tightly coiled molecular geometry necessary for cyclization—at least at the hexa- and heptasaccharide stage.
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