T-Butyl alanine

A solution of 2.0 g of t-butyl alanine (S-form) and 3.78 g of ethyl 2-bromo-4-phenylbutanoate in 25 ml of DMF was treated with 1.8 ml of triethylamine and the solution was heated at 70°C for 18 hours. The solvent was removed at reduced pressure and the residue was mixed with water and extracted with ethyl ether. The organic layer was washed with water and dried over magnesium sulfate. Concentration of the solvent at reduced pressure gave the oily ethyl-a-[(l-carboxyethyl)amino]benzene-t-butanoate. 

A solution of 2.0 g of t-butyl alanine (S-form) and 3.78 g of ethyl 2-bromo-4-phenylbutanoate in 25 ml of dimethylformamide was treated with 1.8 ml of triethylamine and the solution was heated at 70°C for 18 h. The solvent was removed at reduced pressure and the residue was mixed with water and extracted with ethyl ether. The organic layer was washed with water and dried over magnesium sulfate. Concentration of the solvent at reduced pressure gave the oily t-butyl ester of the intermediate which was found to be sufficiently pure by gas liquid chromatography for further use. A solution of 143.7 g of this t-butyl ester in 630 ml of trifluoroacetic acid was stirred at room temperature for one hour. The solvent was removed at reduced pressure and the residue was dissolved in ethyl ether and again evaporated. This operation was repeated. Then the ether solution was treated dropwise with a solution of hydrogen chloride gas in ethyl ether until precipitation ceased. The solid, collected by filtration, was a mixture of diastereoisomers, melting point 153°-165°C. 

The reductive alkylation of methyl pyruvate with and the t-butyl esters of amino acids using Pd/C catalyst leads to the formation of iminodicarboxylic acids such as 67 in selectivities of 29-75% d.e. depending on the amino acid and solvent used (hexane gave the best results). Hydrolysis of the t-butyl ester to the acid 68 followed by hypochlorite-promoted decarboxylation and imine hydrolysis leads to the formation of ( -alanine 69 in correspondingly high e.e.s278,281. The likely decarboxylation mechanism as far as the imine stage is shown in Scheme 65. 

HEMA 2-hydroxyethyl methacrylate VP V-vinyl-2-pyrrolidone TBCM 4-t-butyl-2-hydroxycyclohexyl methacrylate SVC silicone vinyl carbamate VA vinyl alanine NFMA V-formyhnethyl acrylamide EDMA ethylene dimethacrylate MAA methacrylic acid MCOE-PC 2-metha-cryloyloxyethyl-phosphorylcholine. 

As illustrated by the preparation of a-D-glucosyl-(7 )-alanine 75, the method is simple and efficient (Scheme 13). Alkene 72a is treated with iodide 73, sodium cya-noborohydride, and tributyltin chloride in r-butanol to give exclusively the dia-stereoisomer 74 (88%) arising from addition of the glucosyl radical on its a-face followed hydrogen-atom transfer to the intermediate oxazolidinonyl radical anti to the bulky t-butyl group [47]. 

Enantiomerically pure aldehydes 287 were obtained by DIBAL reduction of the corresponding o-alanine methyl esters. Coupling with t-butyl glycinate quantitatively gave the ( )-imines 288 (Scheme 85). Peracid oxidation did not allow the isolation of oxaziridines 289 which spontaneously decomposed to give complex mixtures of products [156]. This was probably due to a deprotonation a to the ester group accompanied by cleavage of the weak N-O bond. Imines 290, derived from aldehydes 287 and P-alanine esters, could be indeed oxidised into stable oxaziridines 291 which were isolated as mixtures of two dia-stereoisomers (Scheme 86) [157]. 

Acetylbenzene. See Acetophenone Acetyl benzoyl. See 1-Phenyl-1,2-propanedione N-Acetyl-N-butyl-P-alanine, ethyl ester. See Ethyl butylacetylaminopropionate Acetyl butyl citrate. See Acetyl tributyl citrate 2-Acetyl-5-t-butyl-4,6-dinitroxylene. See Musk ketone... 

The enzymatic synthesis of peptides (Scheme 6.24) from which proteins can be constructed is not so limited, and chemical synthesis has an even wider application, but these are not yet suitable techniques for manufacture. Moreover, there are no general methods for building the peptides into full protein structures. Nevertheless, enzymes do have a role in the manufacture of peptides themselves. In a mixture of butan-l,4-diol and water, trypsin will catalyse the exchange of the carboxy-terminal alanine of porcine insulin with threonine t-butyl ester (Scheme 6.25). The reaction is essentially a transpeptidation in which the acyl group of lysine is transferred from one amino group on alanine to another on the threonine. This converts porcine insulin into the ester of the human hormone, and a simple deprotection yields one of the commercial products. 

A number of syntheses of (V-hydroxy-a-amino acids and derivatives thereof have been reported. a-Bromocarboxylic acids or their r-butyl esters can be treated with hydroxylamine or 0-alkylated hydroxylamines to give the corresponding hydroxylamine derivatives. yV-Benzyloxy-t-alanine has been obtained by reaction of (/ )-a-bromopropionic acid with O-benzylhydroxylamine. But due to bromide exchange the optical yield was low. Anchimeric assistance of a suitable attached thio group can bring... 

Methyl carbobenzoxy-DL-alaninate heated 2-4 hrs. with fer -butyl glycinate at 80° in molten imidazole, which acts as a catalyst ferf-butyl carbobenzoxy-alanylglycinate. Y 78%. F. e. s. T. Wieland and K. Vogeler, Ang. Gh. 74, 904 (1962) from thiolic acid esters (cf. Synth. Meth. 8, 528) and free amino acids in the presence of water at 40° s. Ang. Gh. 75, 209 (1963) acceleration of p-nitrophenyl ester peptide synthesis (cf. Synth. Meth. 14, 450 75, 343) s. R. H. Mazur, J. Org. Ghem. 28, 2498 (1963) f. bifunctional catalysts s. H. G. Beyerman and W. Maassen van den Brink, Proc. Ghem. Soc. 7905, 266. 

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