Tert-Butoxycarbonyl, protecting group

Hydrogen bromide may be used to remove either the benzyloxycarbonyl or tert butoxycarbonyl protecting group The benzyloxycarbonyl protect mg group may also be removed by catalytic hydrogenolysis... 

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) ... 

The N-tert-butoxycarbonyl protecting group of substituted pyrroles can be removed readily by methoxide ion or, when electron-withdrawing substituents are present, by mild thermolysis.6... 

For example, the tert-butoxycarbonyl protecting group, abbreviated as Boc, is formed by reacting the amino acid with di-tert-butyl dicarbonate in a nucleophilic acyl substitution reaction. 

The replacement of alanine residue by a lysine moiety leads to lisinopril (13-2) administered in this case as a free dicarboxylic acid this compound that is quite active orally in spite of its polarity. The synthesis is quite analogous to that above, involving reductive alkylation of tert-butoxycarbonyl protected lysilprohne (13-1) with ketoester (12-1). Separation of the desired diastereomer followed by the removal of the BOC group with triiluoroacetic acid and then saponification gives lisinopril (13-2) [14]. 

As mentioned in Section 10.6.2, synthesis of 1-hydroxyethylene peptides can be initiated by adding a ferf-butoxycarbonyl N-protected a-amino aldehyde to an optically active Grignard reagent (Scheme 7)J11-13 This reaction affords a diastereomeric mixture of the C4 epimers of the hydroxy ether in good yields. In most cases the mixture is enriched in the 45-epimer and the epimers are readily separable. The yields and the ratios of the resulting 45- and 4R-epimers obtained from several examples of this reaction are summarized in Table 1. When this reaction was attempted with the aldehyde prepared from Aa,Ae-bis-tert-butoxycarbonyl-protected Lys, the desired product was not obtained. The anion of the Lys Ne-tert-butoxy-carbonylamino group probably reacts with the aldehyde to form a cyclic aminol that does not... 

In recent years the tert-butoxycarbonyl (80C) group has achieved a leading role as a protective group for the amino moiety of amino acids in... 

Solvent-free deprotection of the N-tert-butoxycarbonyl (Boc) groups, a very commonly used protection group in organic synthesis, has been accomplished in the presence of neutral alumina that is doped with aluminum chloride (Scheme 2.2-26) [87]. This approach may find application in a typical peptide-bond-forming re-... 

The protecting group Y of the amine is generally an alkoxycarbonyl derivative since their nucleophilicity is low. Benzyloxy- or tert-butoxycarbonyl derivatives usually do not undergo azlactone formation. 

A related N terminal protecting group is tert butoxycarbonyl abbreviated Boc... 

This method is used, for example, for the mild introduction of protecting groups like benzyloxycarbonyl (Z), tert-butoxycarbonyl (Boc) and p-nitrophenylethoxycarbonyl (npeoc). 

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. ... 

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