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Relevant academic research and scientific papers

Sequential One-Pot Synthesis of Dipeptides through the Transient Formation of CDI-N-Protected α-Aminoesters

The synthesis of dipeptides through a sequential one-pot procedure from commercially available protected amino acids is described. The transformation relies on the use of in situ generated transiently CDI-protected α-amino esters (CDI, e.g. N,N′-carbonyldiimidazole). In addition of being a highly atom-economical process, the couplings take place under very mild and neutral conditions without adding a base to the reaction medium. This protocol provides a concise and less costly route to dipeptide derivatives (12 examples, up to 87% yield) and is compatible with commonly used N-urethane protecting groups. Moreover, no epimerization was detected even when sensitive Boc-Cys(Bn)?OH was used. (Figure presented.).

Ethyl 2-cyano-2-(2-nitrobenzenesulfonyloxyimino)acetate (o -NosylOXY): A recyclable coupling reagent for racemization-free synthesis of peptide, amide, hydroxamate, and ester

Ubiquitousness of amide and ester functionality makes coupling reactions extremely important. Although numerous coupling reagents are available, methods of preparation of the common and efficient reagents are cumbersome. Those reagents generate a substantial amount of chemical waste and lack recyclability. Ethyl 2-cyano-2-(2-nitrobenzenesulfonyloxyimino)acetate (o-NosylOXY), the first member of a new generation of coupling reagents, produces byproducts that can be easily recovered and reused for the synthesis of the same reagent, making the method more environmentally friendly and cost-effective. The synthesis of amides, hydroxamates, peptides, and esters using this reagent is described. The synthesis of the difficult sequences, for example, the islet amyloid polypeptide (22-27) fragment (with a C-terminal Gly, H-Asn-Phe-Gly-Ala-Ile-Leu-Gly-NH 2) and acyl carrier protein (65-74) fragment (H-Val-Gln-Ala-Ala-Ile- Asp-Tyr-Ile-Asn-Gly-OH), following the solid-phase peptide synthesis (SPPS) protocol and Amyloid β (39-42) peptide (Boc-Val-Val-IIe-Ala-OMe), following solution-phase strategy is demonstrated. Remarkable improvement is noticed with respect to reaction time, yield, and retention of stereochemistry. A mechanistic investigation and recyclability are also described.

Inverse peptide synthesis via activated α-aminoesters

A mild, practical, and simple procedure for peptide-bond formation is reported. Instead of activation of the carboxylic acid functionality, the reaction involves an unprecedented use of activated α-aminoesters. The method provides a straightforward entry to dipeptides and was effective when a sensitive cysteine residue was used, as no epimerization was detected in this case. The applicability of this method to iterative peptide synthesis was illustrated by the synthesis of a model tetrapeptide in the challenging reverse N→C direction. How to advance by going into reverse: In a mild and practical procedure for peptide-bond formation, free α-aminoesters were activated by treatment with N,N′-carbonyldiimidazole, instead of activating the carboxylic acid functionality (see scheme). The method provided a straightforward route to dipeptides, and its applicability to iterative peptide synthesis was illustrated by the synthesis of a tetrapeptide in the challenging reverse N→C direction.

Polymer-bound triarylphosphine-iodine complexes, convenient coupling reagent systems in peptide synthesis

N-protected α-amino acids are readily coupled with α-aminoacyl esters by polystyryl diphenylphosphine-iodine complex in very high yields and without detectable racemization. Protecting groups of general use for both amine and carboxyl functions, as well a