Carbobenzyloxy group

Reductive alkylation has been used to prepare a-amino acids suitable for lactam formation and further elaboration. In a single step a carbobenzyloxy group was removed, and alkylation with glyoxylic acid hydrate was achieved (18). 

The removal of a carbobenzyloxy group can be separated into two steps (Figure 1). The first step comprises the hydrogenolysis of the benzyl oxygen bond of the Cbz-protected amino acid 1 to form a carbamic acid intermediate 2 and toluene 3. The carbamic acid intermediate decaiboxylates to give the deprotected amino acid 4 and one equivalent of carbon dioxide 5. 

Intermediate diketopiperazine derivatives have been employed in the diastereoselective synthesis of benzyltetra-hydroisoquinoline by 1,4-chirality transfer. iV-Cbz-Proline was coupled with 2-(3,4-dimethoxyphenyl)ethylamine and the resulting amide 109, after deprotection, was reacted with phenylpyruvic acid (Cbz = carbobenzyloxy group). Compound 110 underwent acid-catalyzed Pictet-Spengler condensation to yield final tetracyclic... 

This facile cleavage of the benzyl oxygen bond has made the benzyl group a useful protecting group during multistep synthetic schemes. A particularly important example is the use of the carbobenzyloxy group in peptide synthesis ... 

The most useful protecting group for this purpose is the carbobenzyloxy group. The utility of this group lies in the ease with which it can be removed. Because of the lability of the benzyl C-O bonds towards hydrogenolysis, the amine can be regenerated from a carbobenzyloxy derivative by hydrogenation, which is accompanied by spontaneous decarboxylation ... 

Deprotection of Phosphates, Phosphonates, and Phosphi-nates. BSA has been used in removal of alkyl groups from phosphate, phosphonate, and phosphinate esters to generate the corresponding acids. Conversion of phosphinate ester 99 into phosphinic acid 100 was carried out by treatment with BSA and trimethylsilyl iodide (TMSI), which caused simultaneous removal of the carbobenzyloxy group from the terminal proline residue and of the methyl group from the phosphinate ester (eq 63). Same reaction condition can also allow effective removal of ethyl groups from phosphonate diethylesters. ... 

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