
TY  - JOUR
A1  - Hay, RW 
A1  - Trethewey, RJ 
T1  - The uncatalysed, and the imidazole and o-mercaptobenzoic acid catalysed, hydrolysis of p-nitrophenyl N-benzyloxycarbonylglycinate
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1969
VL  - 22
IS  - 1
SP  - 109
EP  - 119
KW  - 
UR  - https://doi.org/10.1071/CH9690109 
N2  - The uncatalysed hydrolysis of p-nitrophenyl N- benzyloxycarbonylglycinate has been studied in 40% (v/v) ethanol-water over the pH range 7.6-8.5. The reaction shows a first-order dependence on the hydroxide ion concentration. The quite rapid hydrolysis (k = (4.4±0.4) x 104 1. mole-1 min-1 at 20°) may possibly indicate the formation of a 2-benzyloxyoxazoline-5-one intermediate.     Unlike the hydrolysis of the p-nitrophenyl esters of &#945;-amino acids, the hydrolysis of the N-protected derivatives is not catalysed by carbon dioxide. The hydrolysis of p-nitrophenyl N- benzyloxycarbonylglycinate is, however, catalysed by imidazole in 40% v/v ethanol-water. Unprotonated imidazole (Im) is the catalytically active species. N-Benzyloxycarbonylaminoacetylimidazole has been detected spectrophotometrically as an intermediate in the reaction, indicating nucleophilic catalysis by the base. o-Mercaptobenzoic acid was also found to catalyse the hydrolysis of p-nitrophenyl N- benzyloxycarbonylglycinate. pH-rate profile studies indicate that the dianion of o-mercaptobenzoic acid is the catalytically active species, the substrate presumably hydrolysing via the thioester intermediate Z- NHCH2COSC6H4COO-, although efforts to detect such an intermediate have been unsuccessful. Some evidence for a thioester intermediate in the L- cysteine-catalysed reaction has been obtained. 
ER  -

