A new method of glycosylation

Rapid occurrence of sugar tricyclic orthoesters by acid catalyzed intramolecular orthotransesterification

“…One strategy involved the simultaneous esterification of HO-1 and -2 with an orthoacetate followed by regioselective protection at the primary HO-6. For this purpose, compound 2 was prepared as described in literature 8,9 (scheme 1). In an initial protection attempt, orthoacetate 2 was treated with trityl chloride (Ph 3 CCl) in dry pyridine.…”

Classics in Total Synthesis of Oligosaccharides and Glycoconjugates

“…The tertbutyl orthoester fulfills three functions: it insures the protection of positions 1 and 2, a necessary step for the selective synthesis of 81; it reacts with an alcohol under acidic conditions to give a 1,2-trans glycoside, with the concomitant introduction of an acetate function at position 2 (a progenitor of the sulfate group). This is an example of the orthoester procedure nicely developed by the Kotchetkov group in the 1960s [28]. Such a method is rarely used nowadays.…”

Synthetic studies on the trisaccharide intermediate of resin glycoside merremoside H2

“…In order to complete at the same time C-4 glycosylation and rearrangement of the orthoester junction to the required b-glycosidic linkage, 11 was subjected to condensation with monosaccharide imidate donor 3 through glycosyl orthoester glycosylation method. [12][13][14][15] Although this resulted in the formation of trisaccharide 12, the orthoester moiety remained intact under the glycosylation conditions. Moreover, attempts to transform both di-and trisaccharide orthoesters (10 and 12) under various acidic conditions [16][17][18][19][20] into the desired b-glucoside were unsuccessful either.…”