Phenylhydrazine 3-Phenyl hydroxylamine

One approach to unnatural amino acids is to use a readily available amino acid, such as L-phenyl-alanine, as the starting material. The Birch reduction of L-phenylalanine (1) was carried out with lithium in ammonia, followed by acylation of the amino group to produce compound 2, which was further esterihed to produce the cyclohexa-l,4-dienyl-L-alanine derivative 3 (Scheme 11.1). The ozonolysis step of the reaction was carried out at -78°C in a dichloromethane solution presaturated with ozone to reduce the extent of oxidation of the diene 3 to produce 4. Cyclization was then carried out by the introduction of either hydroxylamine hydrochloride to produce the isoxazol-5-ylalanine derivative 5 or phenylhydrazine to give a 1 1 mixture of (l-phenylpyrazol-3-yl)alanine derivative 6 and the (l-phenylpyrazol-2-yl)alanine derivative 7.4,5... 

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