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Method of forming N-protected amino acid thiohydantoins

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TLDR
In this paper, a method of forming a thiohydantoin of formula (II) from an N-protected amino acid (I) is described, which employs a uronium or phosphonium (IV) compound to activate the terminal carboxyl group of the amino acid and a thiocyanate reagent to cyclize the activated amino acid to the thio hydantoin.
Abstract
A method of forming a thiohydantoin of formula (II) from an N-protected amino acid (I) is described. The method employs a uronium (III) or phosphonium (IV) compound to activate the terminal carboxyl group of the amino acid and a thiocyanate reagent to cyclize the activated amino acid to the thiohydantoin. The thiohydantoin can be cleaved from its N-protecting group, for use in C-terminal peptide sequencing. Particularly preferred uronium compounds include salts of 2-chlorouronium. Preferred thiocyanate reagents include trimethylsilyl isothiocyanate and crown ether adducts of metallothiocyanates, such as the 18-crown-6 adduct of KSCN.

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References
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Journal ArticleDOI

New coupling reagents in peptide chemistry

TL;DR: A general synthetic procedure for new derivatives of different N-hydroxy compounds has been developed and these either act as excellent activating reagents causing low racemization during condensation of peptide segments or are useful tools for the formation of active esters suitable for couplings in mixed aqueous / organic media, respectively.
Journal ArticleDOI

PyBOP® and PyBroP: Two reagents for the difficult coupling of the α,α-dialkyl amino acid, Aib.

TL;DR: Coded amino acids could be coupled with Aib using PyBOP under standard conditions of peptide synthesis without racemization whereas the coupling of two Aib residues required PyBroP/DMAP.
Journal ArticleDOI

Sequencing of peptides and proteins from the carboxy terminus

TL;DR: A new chemical method for carboxy- terminal (C-terminal) protein sequencing has been developed and has been successfully used to sequence 5 residues of standard proteins and 5 to 10 residues of synthetic peptides at low nanomole levels.
Journal ArticleDOI

Formation of carboxamides with N,N,N′,N′-tetramethyl (succinimido) uronium tetrafluoroborate in aqueous / organic solvent systems

TL;DR: In this article, the carboxamides were formed using a mixture of N, N,N,N′,N −tetramethyl (succinimido) uronium tetrafluoroborate (TFL) reagents.