Amino acid protecting groups for

Carbamates can be used as protective groups for amino acids to minimize racem-ization in peptide synthesis. Racemization occurs during the base-catalyzed coupling reaction of an A-protected, carboxyl-activated amino acid and takes place in the intermediate oxazolone that forms readily from an A-acyl-protected amino acid (R = alkyl, aryl) ... 

B. Transition Metal-Carbene Complex Residues as Amino-Protective Groups for Amino Acids and Peptides. . . . 11... 

Amino-Protective Groups for Amino Acids and Peptides... 

Adding and Removing Protecting Groups for Amino Acids (28.6)... 

These routine reactions are the basis of the growing numbers of applications of natural amino acids in stereoselective synthesis (Coppola and Schuster, 1987). They are also used for the selective introduction of often exotic structures that are used as protecting groups for amino acids, giving intermediates for peptide synthesis, as illustrated in Chapter 7. 

The blue isomer obtained by irradiation of the well-known photochromic compound 2-(2,4-dinitrobenzyl)pyridine has been identified as the enamine (36) (More O Ferrall and Quirke). There has been a resurgence of interest in photochromic fulgides see e.g. Suzuki et al. Wilcox et al. have de bribed a new photolabile protecting group for amino-acids. An interesting example of intramolecular oxetane formation has been provided by the photoisomerization of indole (37) to (38) (Takechi et al.). 

Table 9.3.2 Protecting Groups for Amino Acid Side Chains...

Adding and removing protecting groups for amino acids (28.7)... 

The phenyl group became a practical protective group for carboxylic acids when Sharpless published a mild, effective one-step method for its conversion to a carboxylic acid. It has recently been used in a synthesis of the amino acid statine, where it served as a masked or carboxylic acid equivalent. ... 

A variant of this method for the introduction of amino protecting groups into amino acids via the alkoxycarbonylimidazolium salts starts from the more reactive carbonyl-bis(methylimidazolium) salts [105]... 

Acts as a catalyst for cleaving the f-Boc protecting group from amino acids in peptide synthesis (Section 26.7). 

Cleavage of protective groups of amino acids. Some amino acid protective groups, for example CBZ and benzyl esters and ethers, are cleaved by palladium black BOC, t-butyl esters, and ethers are stable. If liquid ammonia is used as solvent, the catalyst is not poisoned by sulfur-containing amino acid residues. ... 

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