A route to cyclic peptides and glycopeptides by native chemical ligation using in situ derived thioesters

Applications of Chemical Ligation in Peptide Synthesis via Acyl Transfer

The utility of native chemical ligation (NCL) in the solution or solid phase synthesis of peptides, cyclic peptides, glycopeptides, and neoglycoconjugates is reviewed. In addition, the mechanistic details of inter- or intra-molecular NCLs are discussed from experimental and computational points of view.

The winding pathway to erythropoietin along the chemistry-biology frontier: a success at last

The total synthesis of a homogeneous erythropoietin (EPO), possessing the native amino acid sequence and chitobiose glycans at each of the three wild-type sites of N glycosylation, has been accomplished in our laboratory. We provide herein an account of our decade-long research effort en route to this formidable target compound. The optimization of the synergy of the two bedrock sciences we now call biology and chemistry was central to the success of the synthesis of EPO.

Toward homogeneous erythropoietin: non-NCL-based chemical synthesis of the Gln78-Arg166 glycopeptide domain

Single erythropoietin (EPO) glycoforms with defined mature oligosaccharide structures and amino acid sequences are essential to elucidate the molecular mechanisms by which carbohydrates exert various physiological and metabolic functions and to explore the possible links between carbohydrates and the prevention or management of diseases. To demonstrate that it is possible to generate EPO even without recourse to cysteine-based native chemical ligation, a concise synthesis of the partially protected EPO fragment (78-166) bearing fully mature N- and O-glycans is described.

Toward homogeneous erythropoietin: fine tuning of the C-terminal acyl donor in the chemical synthesis of the Cys29-Gly77 glycopeptide domain

Described herein is the chemical synthesis of the Cys(29)-Gly(77) glycopeptide domain (22) of erythropoietin. Our initial ligation strategy targeted a C --> N termini condensation between glycopeptide 3 and peptide 4. However, the reaction was hindered by the "unattainable" reactivity, mismatched polarity, and severe aggregation of the (glyco)peptide substrates. In contrast, by tuning the C-terminal acyl donor and using smaller peptide fragments, the Cys(29)-Gly(77) glycopeptide domain of erythropoietin was prepared through unconventional N --> C termini condensation reactions. The use of a p-cyanonitrophenyl ester and the development of a masked thiophenyl ester as acyl donors enabled us to promptly access glycopeptides bearing complex carbohydrates and offer potential synthetic applications beyond our current work.

Oxo-ester mediated native chemical ligation: concept and applications

A direct oxo-ester peptide ligation method has been developed. Through the use of an activated C-terminal para nitrophenyl ester (1), it is possible to achieve direct cysteine ligations (1 + 2 --> 4). Peptide substrates incorporating bulky C-terminal amino acids (1) can be accommodated with high reaction efficiency.

Promising agents at the interface of biology and oncology derived through chemical synthesis

This account traces the development of our synthetic glycopeptide- and glycoprotein-based research program over the past decade. We recount the syntheses of a number of biologically relevant, natural product-inspired glycopeptide constructs, including those associated with prostate specific antigen (PSA) and with the gp120 surface envelope protein of HIV. We also describe our progress toward the synthesis of the multiply glycosylated protein, erythropoietin (EPO). Particular emphasis is placed on the development of enabling methodologies which allow for the ligation of complex glycopeptide fragments, thus rendering it possible to access, through purely synthetic means, homogeneous, multidomainal glycopeptide and glycoprotein constructs.

Mature Homogeneous Erythropoietin-Level Building Blocks by Chemical Synthesis: The EPO 114-166 Glycopeptide Domain, Presenting the O-Linked Glycophorin

A synthesis of EPO 114-166 glycopeptide (1), presenting the O-linked glycophorin of erythropoietin, is described.

Iodine catalyzed one-pot diamination of glycals with chloramine-T: a new approach to 2-amino-β-glycosylamines for applications in N-glycopeptide synthesis

Iodine catalyzes a facile one-pot direct diamination of glycals with chloramine-T to afford stereoselectively 2-amino-beta-glycosylamine derivatives that serve as convenient precursors for the synthesis of N-linked glycopeptides.