N-tert Butoxycarbonyl derivatives

The enantioselective nitroaldol reaction of phe-nylalaninals 45 with nitromethane was also promoted with the N-anthracenylmethyl ammonium fluorides in the presence of potassium fluoride.1411 Interestingly, as shown in Scheme 16, the major product was the (2R,3S)-isomer 46a when N,N-dibenzyl-(S)-phenylalaninal and 12 (R=benzyl, X=F) were used while the (2S,3S)-isomer 46b was major when N-tert-butoxycarbonyl derivative 45b and 12 (R=allyl, X=Br) together with potassium fluoride were used. The nitroalcohols 46a and 46b were respectively converted to amprenavir 47a, a HIV protease inhibitor, and its diastereomer 47b. The... 

In the present procedure, pyrrole is brominated under mild conditions to the very labile 2-bromopyrrole using 1,3-dibromo-S.5-dimethylhydantoin the latter reagent gives better results than the previously employed N-bromosuccinimide. Direct conversion of 2-bromopyrrole to Its more stable N-tert-butoxycarbonyl derivative... 

A recent example has been described by Brown et al. who have studied the KR of p-nitrophenyl esters of the d- and i-N-tert-butoxycarbonyl derivatives of glutamine and phenylalanine with ethanol or methanol promoted by chiral lanthanide complexes, providing enantioselectivities of up to 99% ee [302]. On the other hand, an enantioselective hydrolysis of phenylalanine derivatives was reported in 1986, providing a perfect enantiomer discrimination (s> 1000), as a result of catalysis with a tripeptide [303]. In 2007, Maruoka et al. reported the KR of differently a,a-disubstituted a-siloxy aldehydes based on an asymmetric rearrangement into the corresponding chiral acyloins using axially chiral organoaluminium Lewis acids, which provided selectivity factors of up to 39.5... 

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). 

DIASTEREOSELECTIVE SYNTHESIS OF PROTECTED VICINAL AMINO ALCOHOLS (S)-2-[(4S)-N-TERT-BUTOXYCARBONYL-2.2-DIMETHYL-1,3-OXAZOLIDINYL1-2-TERT-BUTYLDIMETHYLSILOXYETHANAL FROM A SERINE-DERIVED ALDEHYDE. 

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... 

Since protein and peptide syntheses are rapidly falling into the hands of organic chemists, four procedures to reach building blocks amino acids in the form of its /8-lactone Na-(BENZYLOXY-CARBONYL)-p-(PYRAZOH-YL)-L-ALANINE and the preparation of both /3-lactones, N-tert-BUTOXYCARBONYL-L-SERINE-p-LACTONE and the p-TOLUENESULFONIC ACID SALT OF (S)-3-AMINO-2-OXE-TANONE are described starting from N-tert-BUTOXYCARBONYL-L-SERINE. A useful S or R serine derivative, 1,1-DIMETHYLETHYL (S) or (R)-4-FORMYL-2,2-DIMETHYL-3-OXAZOLIDINECARBOXYLATEis described followed by the improved preparation of N-(BENZYLOXY-CARBONYD-L-VINYLGLYCINE METHYL ESTER, an important intermediate as well as an important substance in biological processes. 

S-ethyl, 2-(2 -imidazolyl)-4-ethenylphenyl (l-(N-tert butoxycarbonylamino)-2-phenyl) ethylphosphonate, S -0- (N-tert-butoxycarbonyl-L-phenylalanyl) -2-( N-metha-cryloylamino)-3-(5 -imidazolyl) propanol or their derivatives MAA EDMA CH2CI2, CHCI3 or benzene Using substrate analog or transition state analog enantioselective ester hydorolysis of N-tert- butoxycarbonyl phenylalanine p-nitrophenyl ester [173)... 

The reaction of a tryptophan derivative, N- tert-butoxycarbonyl)-L-tryptophan, with hypoxanthine/ xanthine oxidase/Fe(III)-EDTA mainly resulted in the oxygenation of the pyrrole ring of the indole nucleus (Itakura etal. 1994). 2-[(ferf-Butoxy-carbonyl)-amino]-3-(3-indolyl)propionic acid and N- (fer f-butoxycarb onyl) -hT-formylkynurenine were identified as the major products. 

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. ... 

Based on published procedures for preparing both di- and tri-N-protected tert-butoxycarbonyl (Boc) cyclam derivatives [27], we developed the alternate procedure shown in Scheme 2 for obtaining the tri-branched species 11 [28] as well as related procedures for the new tri-branched derivative 12 (see Scheme 3) [28], the linearly linked derivative 13 [28] and the linked cyclic derivative 14 [29], In the case of the phloroglucinol derivative, tri-Boc protected cyclam was first acylated with chloroacetyl chloride the resulting chloromethylamide was then used to trialkylate phloroglucinol in DMF at 70 °C over caesium carbonate as outlined in Scheme 3. Subsequent... 

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