Rao Venkataramanarao

Ultrasound accelerated conversion of Nα-urethane protected peptide esters to their thiopeptides using P2S5

A fast and efficient synthesis of N(alpha)-protected thiopeptide esters from the corresponding peptide esters using P(2)S(5) as thionating agent assisted by ultrasonication has been described. The conversion of peptide bond into thioamide was complete in 20-40 min at rt. The reaction was accomplished without using any base. The products isolated were characterized using (1)H NMR, (13)C NMR and mass spectroscopy.

A Facile Synthesis of C-terminal Neoglycopeptides: Incorporation of Urea Moiety between Sugars and Peptides Employing Curtius Rearrangement

Incorporation of urea moiety in the synthesis of C-terminal neoglycopeptides has been demonstrated through the reaction between suitably protected glycosylamine and Fmoc-peptidyl isocyanates or carbamates. Curtius rearrangement has been made use off for the conversion of peptidyl acid azides in to corresponding isocyanates. The resulting C-terminal neoglycopeptidylureas have been isolated as stable solids which are fully characterized by 1H NMR and mass spectroscopy.

Peptidyl Carbamates: Efficient Synthesis Using N-Fmoc-β-aminoalkoxy Carbonyl Chlorides/Active Pentachlorophenyl Carbonates as Monomeric Building Blocks

A simple protocol for the synthesis of linear peptidylcarbamates employing Fmoc-β-aminoalkoxy carbonyl chlorides is described. The N-Fmoc-β-aminoalkoxy carbonyl chlorides were prepared by the reaction of phosgene or triphosgene with Fmoc-protected β-amino alcohol which were isolated as solids. These oxycarbonyl chlorides were also converted to the corresponding pentachlorophenyl carbonates by reacting with pentachlorophenol. Fmoc-β-aminoalkoxy carbonyl chlorides as well as pentachlorophenol carbonates were successfully used as monomeric building blocks for the synthesis of several peptidyl carbamates.

Synthesis of Ureido-Linked Glycosylated Amino Acids from N α-Fmoc-Asp/Glu-5-oxazolidinones and Their Application to Neoglycopeptide Synthesis

Abstract A simple route for the synthesis of ureido-linked glycosylated amino acids has been described. The key step involves the reaction of isocyanates derived from N α-Fmoc-Asp/Glu-5-oxazolidinones 1 with glycosyl amines followed by hydrolysis. The resulting ureido-linked glycosylated amino acids have been incorporated into peptides. The overall procedure is simple, high-yielding, and involves fewer steps.