Carboxylic acid derivatives tert

A number of nonnatural amino acids were resolved into individual enantiomers on 0-9-(2,6-diisopropylphenylcarbamoyl)quinine-based CSPby Peter and coworkers [48,90,113,114] after derivatization with Sanger s reagent, chloroformates (DNZ-Cl, FMOC-Cl, Z-Cl), Boc-anhydride, or acyl chlorides (DNB-Cl, Ac-Cl, Bz-Cl). For example, the four stereoisomers of P-methylphenylalanine, P-methyltyrosine, P-methyltryptophan, and P-methyl-l,2,3,4-tetrahydroisoquinoline-3-carboxylic acid could be conveniently resolved as various A-derivatives [113]. The applicability spectrum of cinchonan carbamate CSPs comprises also P-amino carboxylic acid derivatives, which were, for example, investigated by Peter et al. [114]. A common trend in terms of elution order of DNP-derivatized P-amino acids was obeyed in the latter study On the utilized quinine carbamate-based CSP, the elution order was S before R for 2-aminobutyric acid, while it was R before S for the 3-amino acids having branched R substituents such as wo-butyl, iec-butyl, tert-butyl, cyclohexyl, or phenyl residues. 

The asymmetric aziridination of a, P-unsaturated carboxylic acid derivatives is a direct route to optically active aza-cyclic a-amino acids, and this class of chiral aziridines can also be used as chiral building blocks for the preparation of other amino acids, P-lactams, and alkaloids. Prabhakar and coworkers carried out an asymmetric aziridination reaction of tert-butyl acrylate with O-pivaloyl-N-arylhydroxylamine 25 in the presence of cinchonine-derived chiral ammonium salt 2e under phase-transfer conditions, which furnished the corresponding chiral N-arylaziridine 26 with moderate enantioselectivity (Scheme 2.24) [46],... 

The catalytic and chiral efficiency of (S,S)-le was also appreciated in the asymmetric synthesis of isoquinoline derivatives, which are important conformationally constrained a-amino acids. Treatment of 2 with a,a -dibromo-o-xylene under liquid-liquid phase-transfer conditions in the presence of (S,S)-le showed complete consumption ofthe starting Schiffbase. Imine hydrolysis and subsequent treatment with an excess amount of NaHCOs facilitated intramolecular ring closure to give 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid tert-butyl ester 38 in 82% yield with 98% ee. A variety of l,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives possessing different aromatic substituents, such as 39 and 40, can be conveniently prepared in a similar manner, with excellent enantioselectivity (Scheme 5.20) [25]. 

Transport peptides can be synthesized using either t-Boc or Fmoc solid phase peptide synthesis strategies with a synthesizer or manually. We routinely synthesize CPPs in a stepwise manner on solid support using an Applied Biosystems Model 431A peptide synthesizer. tert-Butyloxycarbonyl amino acids are coupled as 1-hydroxybenzotriazole (HOBt) esters to a p-methylbenzylhydryl-amine (MBHA) resin (65). C-terminally amidated CPPs are less prone to degradation and show higher internalization efficiency than carboxylic acid derivatives. 

Carboxylic acid derivatives 279 of the pyrrolonaphthyridine series - potential preparations for treatment of degenerative, ischemic and autoimmune diseases -have been synthesized using intramolecular cyclization of ethyl (3-et-hoxycarbonylnaphthyridin-4-ylamino)acetates 280 induced by potassium tert-but-oxide in a toluene BuOII mixture (1994EUP587473). 

The cyclic ketenes were generated fi om A[-acyl-l,3-thiazolidine-2-carboxylic acids by means of Mukaiyama s reagent. The same reaction generated enantio-merically pure 1,3-thiazolidine-derived spiro-p-lactams, using optically active iV-tert-butoxycarbonyl-l,3-thiazolidine-2-carboxylic acid derivatives as precursors of the asymmetrical chiral cyclic ketenes (tert-butoxycarbonyl Boc) [101]. 

Acidic and basic hydrolysis of ethyl 4-oxo-4A-pyrido[l,2-a]pyrimidin-3-carboxylates gave 3-carboxylic acid derivatives (OlMIPl). Stirring tert-butyl ( )-3-(2-hydroxy-8-[2-(4-isopropyl-l,3-thiazol-2-yl)-l-ethenyl]-4-oxo-4Ff-pyrido[l,2-a]pyrimidin-3-yl)-2-propenoate in CF3CO2H at room temperature yielded ( )-3-substituted 2-propenoic acid. 

Tert-Butyl Isocyanide Recently, Ganem and coworkers have reported the first application of CIC in the original P-3CR. They have employed NaN02 (Method A) and N2O4 (Method B) to convert TBIC (Izb) derived secondary amide of the P-3CR product 349 into carboxylic acid derivatives 350 without affecting the existing... 

Shin, C., Y. Sato, and J. Yoshimura a,P-Unsaturated Carboxylic Acid Derivatives. XI. Convenient Synthesis of tert.-Butyl 2-Alkoxy- and Hydroxy-2-acetylamino-3-mono- or 3,3-dihaloalkanoates. Bull. Chem. Soc. Japan 49, 1909 (1976). 

Carboxyl group of (-)-9-fluoro-3-methyl-7-oxo-10-[(3S)-3-(tert-butoxy-carbonylamino)pyrrolidino]-2,3-dihydro-7//-pyrido[l,2,3- 7e]-l,4-benzoxa-zine-6-carboxylic acid was converted into l-nitro-2-oxoethyl group in 45% yield by treatment with l,l -carbonyldiimidazole in boiling CFICI3 for 18h, then with MeN02 in the presence of KOr-Bu for another 18 h (96MI12). 6-(2,2-Diethoxycarbonyl)acetyl derivative formed from the aforementioned 6-carboxylic acid, when it was treated with l,l -carbonyldiimidazole in... 

SYNTHESIS AND RU(II)-BINAP REDUCTION OF A KETOESTER DERIVED FROM HYDROXYPROLINE 2(S)-(p tert-BUTOXYCARBONYL-a-(S) and a-(R)-HYDROXYETHYL)-4(R)-HYDROXYPYRROLIDINE-1 -CARBOXYLIC ACID, tert-BUTYL... 

Scheme 6.92 Generation of the cephalosporin-derived cyclic allene 450 from the cephalosporin / -S-oxide triflate 449 and trapping of450 by (Z)-/J-deuterostyrene, furan, 2-acetylfuran, furan-3-carboxylic acid dimethylamide, N-tert-butoxycarbonylpyrrole, pyrrole and N-methylpyrrole.

Amino group protection may be achieved by converting the amine into its Al-tert-butyloxycarbonyl (tBOC or just BOC) derivative, by reaction with di-tert-butyl dicarbonate. This reagent should be considered as a variant of a carboxylic acid... 

Heating ethyl 5-fluoro-4-[cyano(ethoxycarbonyl)methyl]-2,3-dihydro-l-methyl-7-oxo-l//,7//-pyrido[3,2,l-i7]cinnoline-8-carboxylate (83, R = COOEt) in a mixture of cone. HCl and acetic acid gave the 8-carboxy-4-acetic acid derivative (92EUP470578). The acetic acid group was decarboxylated by heating in boiling ethanol in the presence of NEts to give the 4-methyl derivative. When the 4-[cyano(tert-butoxycarbonyl)methyl]-8-carboxylate 83 (R = COOrBu) was treated with trifluoroacetic acid in methylene chloride at room temperature, the 4-cyanomethyl-8-carboxylate 83 (R = H) was obtained. 

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. ... 

---