Carbobenzoxy group, hydrogenolysis

This Pd catalyst is recommended for deblocking of carbobenzoxy groups by transfer hydrogenolysis (formic acid donor).7... 

Triethylsilane [1, 1218, before references]. Pettit et at. report a case where cleavage of a carbobenzoxy group with triethylsilane—palladium chloride in the presence of triethylamine proceeded in 70% yield. Hydrogenolysis was effected in somewhat lower yield (60%), and the yield obtained by solvolysis with CF3C02H was only... 

JOC2286). Thus, removal of the carbobenzoxy protecting group in (2) by hydrogenolysis in methanol (H2,Pd/C) led to spontaneous cyclization to form (3). 

IsolaHon of anUnes. Amino sugars have been isolated and purified as the N-carbobenzoxy derivatives. The group is removed by hydrogenolysis. Thus Winter-steiner and co-workers isolated crude mycosamine hydrochloride from hydrolysis of the antibiotic nystatin, but were unable to induce the material to crystallize. Reaction with carbobenzoxy chloride in aqueous sodium carbonate and extraction with ethyl acetate gave an oil and, when a solution of this in warm ethanol was chilled and scratched, colorless needles in clusters soon deposited. 

Peptide synthesis. Sheehan and co-workers used this water-soluble reagent for a simplified and rapid synthesis of tetra- and pentapeptides without isolation of intermediates. The reagent (I. I equiv.) is added to a solution of the N-carbobenzoxy-amino acid (I equiv.), the amino acid ester hydrochloride or peptide ester hydrochloride (1 equiv.), and triethylamine (1 equiv.) in methylene chloride. After I hr. at room temperature the solution was washed successively with water (to remove excess reagent and the urea), dilute hydrochloric acid, and sodium bicarbonate solution. The curbobenzoxy group Is removed by hydrogenolysis and the product used directly in the next step. ... 

Formation of the IV-carbobenzoxy derivative of an amino acid for use in peptide synthesis and liberation of the amino group at an appropriate stage of synthesis by hydrogenolysis of the activated CO bond. 

Carbobenzoxy function (CBz) is also an acyl protecting group for the amino function which is removed by hydrogenolysis or under acidic conditions. The chloride is prepared by reaction of benzyl alcohol with phosgene ... 

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