The N-benzyloxycarbonyl group can be THE benzyloxycarbonyl (Z) group,l which can be removed smoothly cleaved under mild conditions, using thio-by hydrogenolysis, is an important amino-protecting group anisole-trifluoroacetic acid, which can deprotect 0in peptide chemistry In the syntheses of the sulphurbenzyltyrosine without the formation of O-to-C re-containing peptides, removal of the N-benzyloxycarbonyl arrangement products, this debloching method was group is accomplished only under drastic conditions such successfully applied to the synthesis of Met-enhephalin as HF,2 H B ~-A c O H , ~ trifluoroniethanesulplionic acid (TFMSA) ,4 methanesulphonic sodium in liquid
The tosyl group attached a t the guanidino function of arginine can be efficiently cleaved by a thioanisole-trifluoromethanesulphonic acid system, which can deprotect 0-2,6-dichlorobenzyltyrosine without the formation of O-to-C rearrangement products ; the NOmesitylene-2-sulphonyl group was also cleaved by a thioanisole-trifluoroacetic acid system. THE tosyl (p-tolylsulphonyl) group in No-tosylarginine, which is one of the most important protecting groups in peptide synthesis, can be removed by HF-anisole,2 but special apparatus is needed.3 Deprotection of Arg(Tos) $ by trifluoromethanesulphonic acid (TFMSA)-anisole is accomplished only under very drastic conditions such as use of a large excess of TFMSA (neat) and a high temperature.* We now report a mild and simple method for removal of the tosyl group attached at the guanidino function of arginine using a thioanisole-TFMSA system,5-* which can deprotect 0-2,6-dichlorobenzyltyrosine and O-methyltyrosine without the formation of O-to-C rearrangement products.6 paThe rate of this cleavage reaction depended on the nature of the nucleophiles used. The promoting effect on the reaction of the nucleophiles examined was in the order: thioanisole > anisole > dimethyl sulphide > phenol -0-
Benzylthyrosin (I) wird durch Thioanisol (III) und Trifluoressigsäure (II) quantitativ in Tyrosin (IV) und das Benzylphenylmethylsulfoniumtrifluoracetat (V) übergeführt.
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