Dl-l-Phenylethylamine

P 9] DL-l-Phenylethylamine and 4-amino-l-benzylpiperidine were dissolved in 0.1 M NaOH aqueous solution [23]. 3-Nitrobenzoyl chloride and 3,5-dinitrobenzoyl chloride were used as ethyl acetate solutions. The concentration of all reactants was set to 0.01 M. Syringe pumps served for liquid feed. The flow rate was 50 plmin and room-temperature processing was applied. No further temperature control was exerted as the reaction is only mildly exothermic. After having passed the micro reactor, the phases were settled in test-tubes and the organic phase was withdrawn for analysis. 

To a mixture of 1,115 parts dl-l-phenylethylamine and 950 parts dimethylformamide are added successively 655 parts triethylamine and 1,130 parts ethyl chloroacetate. After the addition is complete, the whole is stirred overnight. Then there are added 5,600 parts anhydrous ether and the whole is filtered. 

Nitrobenzoyl chloride and 3,5-dinitrobenzoyl chloride were each reacted with dl-1-phenylethylamine and 4-amino-l-benzylpiperidine using a phase-transfer reaction [23]. The amines were in the aqueous phase and the acid chlorides in the organic phase. By this means, a 2 x 2 library was created in one experimental run. 

After the addition is complete, the whole is cooled on an ice bath and there is added dropwise a solution of 144 parts dl-N-formyl-N-[(ethoxycarbonyl)methyl]-l-phenylethylamine in 133 parts ethyl formate. 

The most obvious approach is the resolution of DL-malic acid. This is readily accomplished by forming salts of the racemic acid with (7 )-( -f )-l-phenylethylamine. After filtration of the (i )-( + )-amine salt of L-malic acid, the filtrate is neutralized and the resulting enriched D-malic acid is exposed to ( S)-( — )-phenylethylamine to precipitate the (S)-( — )-amine salt of D-malic acid. Freeing the acid from the amine affords essentially pure D-malic acid (885) in 13% yield [195]. Although the yield is rather low, this resolution can be performed on a large scale, and when one considers that the cost of DL-malic acid is about 60 times less than that of D-malic acid the process is acceptable. 

Spenser and co-workers 123) have investigated the biosynthesis of berberine and related alkaloids elaborated by Hydrastis canadensis L. In separate feeding experiments, D-glucose-i C (uniformly labeled), DL-phenylalanine-2-i4C, DL-tyrosine-2-i4C DL-tyrosine-S-i C, and 3,4-dihydroxy-2-phenylethylamine-l-i4C (dopamine) were administered to the growing plants. Of the compounds tested tyrosine was the most efficient precursor of the major alkaloids, berberine and hydrastine, and dopamine was almost as good. Glucose was a much less efficient precursor, and the incorporation of phenylalanine into these alkaloids was almost negligible. 

Phenylalanine hydroxylase occurs only in mammalian liver (that is, in the rat, guinea-pig, rabbit, d<, chicken, and human) (see also 259). No activity has been observed in (rat) lung, kidney, brain, or muscle. The system is quite speciOc for L-phenylalanine. Tjrro-sine is not formed from n-phenylalanine, nor are the corresponding p-phenols formed from N-acetyl- or N-chloroacetyl-L-phenylalanine, L-phenylalanine ethyl ester, DL-phenylglycine, phenylserine, phenylpyruvic acid, phenylethylamine, benzoic acid, hippuric acid, cinnamic acid, or mandelic acid (768), or from aniline, acetanilide, tryptophan, kynurenine, anthranilic acid, or phenylacetate (557). This specificity is a distinguishing character of the enzyme, which occurs in the same tissue as the nonspecific aromatic hydroxylase described above. 

---