T-butyloxycarbonyl group

The two commonest examples are the benzyl carbamates (CBZ derivatives) (4) and the t-butyl carbamates (BOC derivatives) (5) where the amino group is protected by the benzyloxycarbonyl or the t-butyloxycarbonyl groups respectively. 

The conversion of the amino group in amino acids into a t-butyloxycarbonyl group is a process which is widely used in automated peptide synthesis carried out on solid (polymeric) supports (solid phase synthesis the Merrifield technique).230... 

The 2,2,2-trichloroethoxycarbonyl group is stable to acid, but somewhat labile to base. A superior protective group is the 2,2,2-trichloro-t-butyloxycarbonyl group, which is stable to both acid and base. The group is introduced by means of the stable chloroformate, prepared from chloretone (equation II). This protecting group is cleaved by the anion 2 in about 1 minute in approximately 90% yield. It is also... 

Another readily available and potentially useful chiral reagent that has received very little attention is T-butyloxycarbonyl-L-leucine-N-hyroxy-succinimide ester, [12]. This reagent was used to acylate the amino group of the chiral drug y-vinyl- v-aminobutyric acid, followed by trifluoroacetic acid-catalyzed removal of the t-butyloxycarbonyl group (63). The dia-stereomeric derivatives were resolved on a C8 column, with an a value as... 

Some reactions can be driven to completion by removing the products physically from the reaction. Products that are out of solution may be protected from further reaction. An excellent example is found for the selective removal of the Boc (t-butyloxycarbonyl) group from N-Boc-amino acid t-butyl esters [37]. As shown in Figure 4.14, treatment of the L-serine derivative 18 with anhydrous HC1 in... 

F irther worl l with the t-amyloxycarbonyl group showed that it is comparable to the t-butyloxycarbonyl group. The furfuryloxycarbonyl group was foTind to be between the t-butyloxycarbonyl and benzyloxycarbonyl groups in ease of removal by acid treatment. 2... 

Mc3SiCI/phenol provides for the selective deprotection of the N-t-butyloxycarbonyl group in solid phase peptide synthesis, and Mc3SiQ/DMSO converts benzylic alcohols to styrenes and the oximes and semicarbazones of a,P-unsaturated ketones and aldehydes to the... 

Halotriazoles can act as halogenating agents and A-acyltriazoles can act as acyl transfer reagents. Triazole can be used for the synthesis of peptide bonds and is superior to imidazole in that less racemization is observed. It can also be used to transfer the t-butyloxycarbonyl (t-Boc) protecting group to the nitrogen of amino acids. For details see Polya <84CHEC-I(5)733, p. 786). 

Phase-transfer catalysed N-alkylation of diphenylphosphinic amide (I) is totally unsuitable in the case of easily hydrolysable organic halides, especially those containing additional functional groups (i.e. carbonyl or carboalkoxyl) which decompose readily in strongly alkaline medium. To circumvent the difficulty connected with simultaneous mono- and dialkylation of (I) under anhydrous conditions, N-(t-butyloxycarbonyl) diethyl phosphoroamidate (X), a doubly-protected ammonia derivative, was devised as a useful and superior substitute of phthalimide in the Gabriel-type synthesis of amines. 

A close relative to Cbz is Boc (t-butyloxycarbonyl) that uses a different method to make esters easy to hydrolyse. It is added to an amine or an alcohol by the chloroformate 46 and, after the reaction, hydrolysed with acid—no water being needed. The ester is protonated and the t-butyl cation drops out in an Sn 1 reaction 49 to give the same intermediate 36 as in the removal of the Cbz group. 

X amino-protecting group (e.g. t-butyloxycarbonyl) Y activating group (e.g. —N3, —C6H4-p-N02,... 

This new method of catalytic oxyamination is more effective than the chloramine-T based procedure with electron-deficient alkenes such as dimethyl ( )-2-butenedioate, but less effective with trisubstituted alkenes. However, a major advantage is that the nitrogen is now introduced bearing the more easily removed benzyloxycarbonyl and tm-butyloxycarbonyl groups. 

Characterization or N-protection of amino acids by the f-butyloxycarbonyl group can be carried out either by acyl transfer from the triazole (335) prepared as in Scheme 144 or with t-butyl phenylcarbonate in the presence of triazole (73TL469) in lower yields. Although 1,2,4-triazole acts as a catalyst in the second of these reactions, it has to be present in an equimolar amount. 

AMINO GROUP Boron trifluoride ether-ale. l-r-Bulyloxycarbonyltriazole-1,2,4, Di-t-butyl dicarbonate. 4-Dimethylamino-1-t-butyloxycarbonyl pyridinium chloride. CARBONYL GROUP Ceric ammonium nitrate. 1,2-Dihydroxy-3-bromopropane. Sodium N-chloro-p-toluenesulfonamide. Thallium(lll) nitrate. Trichloroethanol. Trimcthylsilyl cyanide. Chloromethyl methyl sulfide. N,N -Diisopropylhydra-zinc. Trichloroethanol. 

The next amino acid in the peptide is methionine, and it will of course need N-protecting and C-activating. The N-protecting group used this time was different—stiU a carbamate, not Cbz or Z but t-Boc (or just Boc or BOC)—standing for t-butyloxycarbonyl and pronounced bock or... 

N Protectlve group in peptide synthesis. The reagent provides a new and improved method for the preparation of N-t-butyloxycarbonyl derivatives of amino acids or peptides, since it reacts with the NHj group with elimination of HCN to form the derivative, as illustrated for L-leucine ethyl ester. The reactants are mixed at (f and agitated at room temperature for 1 hr. The solvent is evaporated and the product isolated from the dried neutral fraction. 

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