3- Hydroxy-4-methoxy phenylalanine

Entacapone and tolcapon are selective and reversible catechol-O-methyltransferase (COMT) inhibitors which also inhibit the break down of levodopa to 3-methoxy-4-hydroxy-L-phenylalanine. 

Hydroxy-3-methoxy-L-phenylalanine reacts with xenon difluoride to form after acidic hydrolysis by hydrogen bromide 6-fluoro-3,4-hydroxy-i.-phenylalanine (6-F-DOPA) in 25 % yield.66... 

Phenol, 5-methoxy-3-[2-(3-hydroxy-4-methoxy-phenyl)-ethylj Lf 1.9 3209 Phenylalanine 1 3172 Phloriglucinol, P-D-glucoside St ° Phosphatase, adenosine-5 1 3172 Phosphoric acid 1 3172 Phthalate, N-butyl 0 ... 

The conversion of phenylalanine, a C-6—C-3 precursor, to the C-6—C-1 unit of the Amaryllidaceae alkaloids requires the formal loss of two carbon atoms from the side chain of the amino acid as well as the introduction of at least two oxygenated substituents into the aromatic ring. The results shown in the latter part of Table III emphasize the specificity of the C-6—C-1 precursor. Benzaldehyde, -hydroxybenzal-dehyde, isovanillin, and protocatechuic acid are not incorporated to any appreciable extent into the alkaloids, while cinnamic, -hydroxy-cinnamic and caffeic acids, protocatechuic aldehyde, and 3-hydroxy-4-methoxy-i C-A-methyl-i4( ., enzylamine readily become part of the C-6—C-1 unit. 

Catecholamines and their metabolites The catecholamines, adrenaline, noradrenaline, and dopamine are essential components of the central nervous system acting as neurotransmitters both within the brain and at peripheral nerves. All are synthesized in the adrenal medulla from phenylalanine or tyrosine and are metabolized by a mixture of enzymatic side chain oxidation and methylation of the hydroxy groups on the ring. If the metabolism is complete, adrenaline and noradrenaline are degraded to 4-hydroxy-3-methoxy mandelic acid (HMMA, commonly called vanillylmandelic acid - VMA), while dopamine is broken down to homovanillic acid (HVA). Urinary excretion of these metabolites and their conjugates is the major route of elimination of catecholamines from the body, although small amounts are excreted unchanged as the free catecholamines. 

VON Studnitz, W., Occurrence, isolation and identification of 3-methoxy-4-hydroxy-phenylalanine, Clin. Chim. Acta 6, 526 (1961). 

De Paolis, M., Chen, X., and Zhu, J. (2004) A short enantioselective synthesis of protected I-3-hydroxy-4-methoxy-5-methyl phenylalanine and its corresponding aldehyde - a common subunit of ecteinascidin-743, safradn and congeners. Synlett, 729-731. 

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