Butoxycarbonyl protecting

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... 

Ester group of l-(ethoxycarbonylmethyl)-7-aryl-5-oxo-1,2,3,5-tetrahydro-pyrido[l,2,3-i/e]quinoxaline-6-carboxamides was hydrolyzed and the 1-carboxymethyl moiety was converted to an aminocarbonylmethyl group with 1-methylpiperazine (01MIP12). Bromo atom of l-(2-bromoacetyl) derivatives was substituted by different amines. An amino group in the side chain attached to the position 1 of 7-aryl-5-oxo-l,2,3,5-tetrahydropyr-ido[l,2,3-i/e]quinoxaline-6-carboxamides was acylated, and terc-butoxycarbonyl protecting group of amino group was eliminated. 

The PEB temperature and temperature uniformity must be tightly controlled for the same reasons discussed above. It has been found that it is feasible to drive the deprotection reaction in t-butoxycarbonyl protected systems to completion, providing the side reactions are minimized or controlled. This is a necessary requirement for satisfactory lithographic performance. 

A Mehta, R Jaouhari, TJ Benson, KT Douglas. Improved efficiency and selectivity in peptide synthesis use of triethylsilane as a carbocation scavenger in deprotection of t-butyl and t-butoxycarbonyl-protected sites. Tetrahedron Lett 33, 5441, 1992. 

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]. 

N-Alkylatum of Benzyloxycarbonyl- and fert-Butoxycarbonyl-Protected Amino... 

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... 

Dunach has reported the insertion of the heterocumulene into N-Boc (Boc = t-butoxycarbonyl) -protected 2-subshtuted aziridines under mild conditions (ambient temperature, atmospheric C02 pressure), using electrochemical methods and dibromo(l,4,8,ll-tetraazocyclotetradecane)-nickel(II), NiBr2(cyclam), as catalyst (10mol%) [68m]. However, the process was poorly selective as a mixture of 4- and 5-regioisomers was obtained in all cases investigated. 

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) ... 

Note Boc, -butoxycarbonyl, protecting group is stable to the reaction conditions in Steps 1-6.)... 

Scheme 4.8. Poly(propylene imine) dendrimers that have been terminally functionalized with rert-butoxycarbonyl protected phenylalanine units. These macromolecules were described as dendritic boxes due to their ability to entrap guests. R = benzyl (20) hydrogen atoms are omitted in the structures.

Denkewalter et al. 4 synthesized a series of terf-butoxycarbonyl-protected poly(a,e-L-lysine) macromolecules (see above, Scheme 4.3), whose molecular models suggested them to be globular, dense spheres and whose molecular weight distribution was determined to be very narrow (MJM = 1.0). Since each generation in this series was synthesized in a stepwise manner, each member was predicted to have a monodisperse molecular weight. 

Figure 14.44 also shows how the Curtius degradation of an acyl azide can be combined with the addition of ferf-butanol to the initially obtained isocyanate. This addition gives a carbamate. In the present case a fert-butoxycarbonyl-protected amine ( Boc-protected amine ) is formed. 

Polymer supported carbodiimides are also used in the reaction of N,N -bis(t-butoxy-carbonyl)thiourea with polymer supported triamines to give N,N -bis(t-butoxycarbonyl)-protected guanidines." " ... 

Cleavage of carbamates. N-Benzyloxy- and N-r-butoxycarbonyl protected peptide derivatives can be selectively cleaved by reaction with ISilCHsls at 25-50° in the presence of side-chain blocking groups such as methyl esters or benzyl ethers. 

A-rerr-Butoxycarbonyl-Protected Amino Acid Perfluorophenol Esters General Procedure 6... 

Other peptides in the Fcycto-MRF-NH2 series have been prepared using a more acid stable resin (MBHA, methoxybenzhydry-lamine) and Boc (t-butoxycarbonyl) protecting groups, but the Fmoc approach above gives superior yields. ... 

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

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