Amino acids, synthesis phenylhydrazone

Amino acid synthesis. Phenylhydrazones of x-keto acids (I, prepared by reaction of a phenyldiazonium salt with a reactive methylene group, the Japp-Klingemann reaction ) are readily hydrogenated with 5 % Pd/C (also platinum) to give amino acids (2). 

Amide reduction with lithium aluminum hydride, 39, 19 Amine oxide formation, 39, 40 Amine oxide pyrolysis, 39, 41, 42 -Aminoacetanilide, 39, 1 Amino adds, synthesis of, 30, 7 2-Amino-4-anilino-6-(chloro-METHYl) -S-TRIAZINE, 38, 1 -Aminobenzaldehyde, 31, 6 hydrazone, 31, 7 oxime, 31, 7 phenylhydrazone, 31, 7 > -Aminobenzoic add, 36, 95 2-Aminobenzophenone, 32, 8 c-Aminocaproic acid, 32, 13 6-Aminocaproic acid hydrochloride,... 

The second example is an interesting synthesis of the heterocyclic amino acid tryptophan (R = 3-indolymethyl) which involves the initial base catalysed 1,4-addition (the Michael reaction, Section 5.11.6, p. 681) of diethyl acetamido-malonate to the oc,/ -unsaturated aldehyde, acrylaldehyde, yielding the aldehydic derivative (38). The derived phenylhydrazone (39) is then cyclised under acidic conditions (see Expt 8.26) to form the indolylacetamidomalonate derivative (40) which is then converted into the corresponding a-amino acid (i.e. tryptophan) in the usual way (Expt 5.184). 

Another practicable synthesis of alanine has been described recently by Billman and Parker (97, 99). Alanine is prepared in 45% of the theo retical yield by permanganate oxidation of commercially available 2-ben> zoylamino-l-propanol and acid hydrolysis of the resulting benzoyl-alanine. Other syntheses which are of value for special purposes, such as the introduction of isotopic atoms into amino acid molecules, include the catalytic reduction of the phenylhydrazone of pyruvic acid (264,272,298) and of a-oximinopropionic acid (366, 718). 

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