Tert-Butoxycarbonyl group protecting amines with

The alkoxycarbonyl protecting groups can also be introduced into amines by, triazolides (Table 4—7). With A-tert-butoxycarbonyl-1,2,4-triazole the tert-butoxy-carbonyl protecting group (Boc) is transferred readily onto amino functions of primary amines, trimethylbenzyl ammonium salts of amino acids, or peptides.[ 1965 Alternatively, the Boc group can be transferred with terf-butylphenylcarbonate in the presence of 1,2,4-triazole. In this latter approach the triazolide is presumably formed as an intermediate. ... 

N-Acylation and 3-alkoxycarbonylation reactions may be achieved by conventional acylation procedures. A variety of 3-acyl derivatives 157 can be prepared most conveniently by the treatment of DPPOx 266 with carboxylic acids in the presence of a tertiary amine. tert-Butoxycarbonyl (Boc-Ox, 236) and benzyloxy carbonyl (Cbz-Ox, 267) (Cbz = benzyloxycarbonyl) compounds are of practical use for introduction of nitrogen protecting groups. ... 

The key starting material of one of the first antagonists, argatroban (30-6), comprises a derivative of arginine itself in which the amine is protected as its tert-butoxycarbonyl derivative and an A-nitro group moderates the basic nature of the guanidine group (30-2). That intermediate is first condensed with the piperidine... 

Yamashiro et al. 1972), boron trifluoride etherate in acetic acid (Schnabel et al. 1971), trimethylsylil triflate (Schmidt et al. 1987), trimethylsilyl perchlorate (Vorbrueggen Krolikiewicz 1975), and, most frequently, trifluoroacetic acid (Farowicki Kocienski 1995 and references therein). Deprotection of the /-HOC group under neutral conditions was not described until recently, yet it is highly desirable. Now it has been found that the tert-butoxycarbonyl protecting group for amines, alcohols, or thiols is removed efficiently (90-99% yield) with use of 0.2 equivalent of cerium ammonium nitrate in acetonitrile at 80°C (Hwu et al. 1996) ... 

Peptide synthesis is made possible by the use of selective protecting groups. An N-protected amino acid with a free carboxyl group is coupled to an 0-protected amino acid with a free amino group in the presence of dicyclo-hexylcarbodiimide (DCC). Amide formation occurs, the protecting groups are removed, and the sequence is repeated. Amines are usually protected as their tert-butoxycarbonyl (BOO derivatives, and acids are protected as esters. This synthetic sequence is often carried out by the Merrifield solid-phase technique, in which the peptide is esterified to an insoluble polymeric support. 

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