Synthesis of (2R)- and (2S)-aminooxy analogues of β-O-glucosylserine andN-oxyamide linked glycoconjugates

Abstract

Glycosyl amino acids are constituents of glycopeptides and glycoproteins playing important roles in various cellular activities and pathogenic processes. We have stereoselectively synthesized both (2R)-and (2S)-aminooxy analogues of b-O-glucosylserine from sn-(3-b-O-glucosyl)glycerol through selective protection, Mitsunobu reaction, oxidation and Lattrell-Dax epimerization reactions. N-oxyamide linked glycopetides and glycolipids have been prepared from the b-O-glucosyl aminooxy acid derivatives. 1 H NMR and IR studies suggest the formation of an a NÀO turn structure in the glycopeptide 19.

N–O linkage in carbohydrates and glycoconjugates

“…240 O-Glucosylated (2R)-2-aminooxy acid has also been synthesized from O-amino β-glucoglycerol 125, through oxidation of primary alcohol after desilylation (Scheme 26c). 241 The O-glucosylated (2S)-2-aminooxy acid 134 has been stereoselectively prepared either through double inversions of the C-2 configuration in 124 with Lattrell-Dax epimerization reaction followed by Mitsunobu reaction with acid exhibited a selective binding affinity towards the chloride ion, and formed a nanomolecular assembly (nanorods) through intermolecular hydrogen-bonding at higher concentration. 243 For the development of new foldamers, Chandrasekhar and colleagues have synthesized cis-β-furanoid sugar aminooxy acid as a building block to obtain their short homo-oligomers which exhibited rigid ribbon-like secondary structures favouring 5/7 bifurcated intramolecular hydrogen-bonded rings (Scheme 27a).…”

“…The phthaloyl group in 135 was removed by hydrazinolysis to 136, then converted to glycopeptide mimics as in 137 and 138. An α-turn structure has been observed in the glycopeptide 138 (Scheme 26d) 241. Syntheses of C-glucosyl α-aminooxy esters 142 and 143 were achieved from α-C-allyl glucoside 139, through dihydroxylation to separable diols 140 and 141, followed by selective protection, Mitsunobu reaction, deprotection and oxidation reactions (Scheme 26e) 242.…”

Synthesis of O-Amino Sugars and Nucleosides

“…For the O -glycosyl aminooxy acid derivatives, we have stereoselectively synthesized both (2 R )- and (2 S )-aminooxy analogues of β- O -glucosylserine from sn -(3-β- O -glucosyl)glycerol 39 which was obtained through glycosylation of sn -1,2-di- O -benzyl-glycerol with d -glucose pentaacetate followed by debenzylation (Scheme 7) [30]. Selective silylation and Mitsunobu reaction with PhthNOH and acidic desilylation afforded the sn -(2- O -phthalimido-1- O -glucosyl)glycerol 41 which was transformed into the (2 R )-3-β- O -glycosyl aminooxy ester 42 after selective deprotection of phthaloyl group with 1.1 equivalent of hydrazine in methanol during 20 min at 0 °C.…”

“…Three β-glucolipids bearing one lipid chains 61 – 63 have also been obtained from 40 . Coupling of octanoic acid with the glucosyl aminooxy ester 42 led to glucolipid 64 [30]. …”