132682-03-2Relevant academic research and scientific papers
New reactions of the thiocarbonyl function. The synthesis of hindered peptides
Barton, Derek H. R.,Ferreira, J. Albert
, p. 1 - 20 (2007/10/03)
The well-known radical chemistry of the thiocarbonyl function has been expanded to include the concerted reaction between an O-acyl derivative of N-hydroxypyridine-2(1H)-thione (a Barton PTOC ester) and a sulfenamide. The atom-economical process spawned a carboxamide and an unsymmetrical disulfide of synthetic and biological value. The reaction was successfully applied to the synthesis of sterically encumbered, urethane-protected dipeptides. The oxidation-reduction technology pertaining to the disulfide-phosphine combination facilitated the generation of transient Barton PTOC esters. In conjunction with the appropriate benzenesulfenamide, the Barton PTOC ester of benzoyl-L-leucine was shown to preserve optical integrity according to the sensitive Young test, albeit at low temperature. However, the thermodynamic forces at play are powerful and, as a result, the yields were not compromised. In all but the sterically demanding instances, the parent free amine almost matched the reaction time, yield, and enantiomeric excess of the corresponding benzenesulfenamide in its reaction with a Barton PTOC ester.
N-hydroxypyridine-2(1H)-thione derivatives of carboxylic acids as activated esters. Part II. Applications in peptide synthesis
Barton, Derek H. R.,Ferreira, J. Albert
, p. 9367 - 9386 (2007/10/03)
The N-hydroxypyridine-2(1H)-thione derivatives of two urethane-protected α-amino acids readily reacted with the α-amino acid esters or the corresponding benzenesulfenamides to give simple dipeptides in reasonable yields. The benzenesulfenamides are the re
PyBOP and PyBroP: Two reagents for the difficult coupling of the α,α-dialkyl amino acid, Aib
Frerot, Eric,Coste, Jacques,Pantaloni, Antoine,Dufour, Marie-Noelle,Jouin, Patrick
, p. 259 - 270 (2007/10/02)
The difficult coupling of α-aminoisobutyric acid (Aib) was carried out using PyBOP and PyBroP in a comparative study with BOP and BroP. These reagents gave good results under simple conditions (one pot, r.t., 1h). 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. A fragment containing an Aib C-terminal could be coupled without epimerization of the penultimate residue.
