127656-85-3

3-Mercaptopropionic acid and Fmoc amino acids, having unprotected carboxyl groups, were glycosylated with sugar 1,2-trans-acetates in 90 and 53-65% yields, respectively, under lewis acid promotion. The synthesis of a neoglycopeptide illustrates the use of the building blocks in solid phase peptide synthesis.

The synthetic glycopeptides are interesting model systems to study the effect of O-glycosylation in modulating their function and structure. A series of glycosylated analogs of two antibacterial peptides, formaecin I and drosocin, were synthesized by varying the nature of sugar and its linkage with bioactive peptides to understand the influence of structure variation of glycosylation on their antibacterial activities. Higher antibacterial activities of all glycopeptides compared to their respective non-glycosylated counterparts emphasize in part the importance of sugar moieties in functional implications of these peptides. The consequences of the unique differences among the analogs were apparent on their antibacterial activities but not evident structurally by circular dichroism studies. We have shown that differently glycosylated peptides exhibit differential effect among each other when tested against several Gram-negative bacterial strains. The change of monosaccharide moiety and/or its anomeric configuration in formaecin I and drosocin resulted into decrease in the antibacterial activity in comparison to that of the native glycopeptide, but the extent of decrease in antibacterial activity of glycosylated drosocin analogs was less. Probably, the variation in peptide conformation arising due to topological dissimilarities among different sugars in the same peptide resulting in possible modulation in binding properties appears to be responsible for differences in their antibacterial activities. Indeed, these effects of glycosylation are found to be sequence-specific and depend in the milieu of amino acid residues. Interestingly, none of the carbohydrate variants affected the basic property of these peptides, which is non-hemolytic and non-toxicity to eukaryotic cells. The Author(s) 2011.

Oxytocin structure was modified in position 4 using glycoamino acids. Procedure for transformation of Fmoc-protected serine and threonine derivatives into appropriate O-glycosylated precursors suitable for solid phase peptide synthesis (SPPS) was worked o

Glycosylation of Fmoc-hydroxyamino acids with β-D-glucose pentaacetate has been carried out in the presence of several Lewis acids and BF3.Et2O has been found to be the most suitable one. Thus, 2,3,4,6-tetra-O-acetyl-β-D-glycopyranosyl derivatives of Fmoc-Ser/Thr/Tyr are prepared in a single step in reasonably good yields and high purity. The O-glycosylated derivatives are then converted to their corresponding trichlorophenyl esters for use in the solid phase synthesis of five glycoopioid peptides related to dermorphin. The effect of glycosylation on biological activity of dermorphin has been studied. Among the peptides synthesized, [Tyr(β-D-Glc)5]dermorphin and [Ser(β-D-Glc)5, Tyr7)]dermorphin exhibit considerable analgesic activity of about 80-90% compared to morphine and antidiarrhoeal activity of about 50% compared to dermorphin.

Nα-Fmoc amino acids with an unprotected α-carboxyl group have been glycosylated with carbohydrate 1,2-trans peracetates using Lewis acids as promoters.Aliphatic and phenolic O- and S-glycosides of amino acids, with a 1,2-trans anomeric configuration, were obtained as products in 34-65percent yields.The glycosylated building blocks have the protective groups of choice (i.e.O-acetyl and Nα-Fmoc) for direct use in stepwise synthesis of glycopeptides.The starting materials are readily available and the method does not require an extensive experience in synthetic carbohydrate chemistry.

The building blocks O1-(2,3,4,6-tetra-O-acetyl-β-D- galactopyranosyl)-Nα(fluoren-9-ylmethoxycarbonyl)serine (5)and O 1-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl) -Nα-(fluoren-9-ylmethoxycarbonyl)threonine (6) for use in solid-phase glycopeptide synthesis can be obtained via their ally esters by mild treatment with tetrakis(triphenylphosphine)palladium(0) and tributyltin hydride with no Fmoc elimination or sugar cleavage or anomerization.