N-tert-butoxycarbonyl groups

This approach may find application in peptide bond formation that would eliminate the use of irritating and corrosive chemicals such as trifluoroacetic acid and piperidine as has been demonstrated recently for the deprotection of N-boc groups (Scheme 6.7) a solvent-free deprotection of N-tert-butoxycarbonyl group occurs upon exposure to microwave irradiation in the presence of neutral alumina doped with aluminum chloride (Scheme 6.7) [41]. 

Scheme 8.10. Deprotection of N-tert-butoxycarbonyl group on alumina.

The Baran group has reported an unusual deprotection of allyl esters in micro-wave-superheated water. A diallyl ester structurally related to the sceptrin natural products (see Scheme 6.87) was cleanly deprotected at 200 °C within 5 min (Scheme 6.168) [181]. Other standard deprotection transformations carried out under microwave conditions, specifically N-detosylations [317], trimethylsilyl (TMS) removal [318, 319], and N-tert-butoxycarbonyl (Boc) deprotection [231], are summarized in Scheme 6.169. 

Pyrrole and its simple derivatives do not react easily as dienes. Pyrrole itself only combines with dimethyl acetylenedicarboxylate (DMAD, dimethyl but-2-ynedicarboxylate) under high pressure and then it is by C-2 substitution. However, A-acylpyrroles, such as A-acetyl- and N- tert-butoxycarbonyl)pyrrole, do undergo Diels-AIder addition reactions. Here, internal resonance within the acyl group reduces the availability of the lone-pair electrons, formally on nitrogen, to delocalize into the ring, thus making the carbon unit more diene-like (Scheme 6.12). 

One of the most investigated type of reaction in the field of catalytic imprinted polymers, as indicated by the large number of publications available, is certainly ester hydrolysis. In particular, a great deal of work has been carried out on systems inspired by hydrolytic enzymes since 1987. In 2000, Shea et al. [37] reported the preparation of enantioselective imprinted polymers for the hydrolysis of N-tert-butoxycarbonyl phenylalanine-p-nitrophenyl ester (55), using a system already developed by the same group in 1994 [19]. The system was inspired by the natural hydrolytic enzyme chymotrypsin and polymerisable imidazole units (27) were used as functional monomers coupled via ester linkages to a chiral phosphonate (56), analogue of (d)- or (L)-phenyl-alanine. After template removal, the imprinted polymers showed selectivity towards the hydrolysis of the enantiomer with which they were imprinted. The ratio of the rate constants, k /k, was 1.9 for the polymer imprinted with the D-enantiomer and kjku was 1.2 for that imprinted with the L-enantiomer. Moreover, the imprinted polymer showed a 2.5-fold increase in the rate of the reaction when compared with the control polymer, imprinted with a... 

Rather more conventional means were used to remove an alkyl silyl ether in the presence of an ary silyl ether in a synthesis of Dynemicin Here the task was simply accomplished with HF in acetonitrile [Scheme 4.56].92 Acidic conditions also prevailed in a synthesis of Doliculide wherein an alkyl tert-butyl ether, a tert-butyl ester and an N-fert-butoxycarbonyl group were cleaved simultaneously without challenge to the remaining aryl silyl ether [Scheme 4.57] ... 

The procedure described here offers a general route to 7-substituted indolines.3 The method is based on the directed ortho-lithiation of N-(tert-butoxycarbonyl)aniline derivatives.4 The teri-butoxycarbonyl group seems to be essential for C-7 selective lithiation, since other directing groups so far reported promote C-2 metalation on the Indoline ring.5 The C-7 selective lithiation of 1-(tert-butoxycarbonyl)indoline is in contrast to the C-2 selective lithiation of 1-(tert-butoxycarbonyl)indole.6... 

Finally, acylation of the amine 9g with acetyl chloride in the presence of N,N-diisopropylethylamine affords compound 9b. The saponification and acidic removal of the tert-butoxycarbonyl groups of 9h complete the synthesis of 9 as a trifluoroacetic acid salt. 

Afonso, C. A. M. Transformation of an azido group to an N-(tert-butoxycarbonyl)amino group via the Staudinger reaction. Synth. Common. 1998, 28, 261-276. 

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... 

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-... 

A 0.34 M benzene soln. of N-(trifluoroacetoxy)succinimide in methylene chloride added dropwise with stirring over 2 h to a soln. of N -(r rr-butoxycarbonyl)-N -benzylspermine in the same solvent at 0°, and stirring continued for 2 h - N - tert-butoxycarbonyl)-N -benzyl-N -(trifluoroacetyl)spermine. Y 82%. Sec. amino groups remain unaffected. F.e.s. R.J. Bergeron, J.S. McManis, J. Org. Chem. 53, 3108-11 (1988). 

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

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