Phenylalanine and derivatives

As for photochemistry, aliphatic amines are photodegraded over titanium dioxide, and the nitrogen is found mainly as ammonium cation. The complex issue of H elimination from aminoacids has been confronted by experiments and computation, a recent example referring to phenylalanine and derivatives. A detailed mechanistic analysis of the H loss from aniline... 

Prell JS, Chang I M, O Brien JT, Williams ER (2010) Hydration isomers of protraiated phenylalanine and derivatives relative stabilities from infrared photodissociatitui. J Am Chem Soc 132 7811-7819... 

With phenylalanine and tyrosine, the sodium salt of the derivative is sparingly soluble in water and separates during the initial reaction. Acidify the suspension to Congo red the salts pass into solution and the mixture separates into two layers. The derivative is in the etheresil lay and crystallises from it within a few minutes. It is filtered off and recrystaUised. 

Protect glycine as its Boc derivative and anchor this to the solid support Remove the pro tecting group and treat with Boc protected phenylalanine and DCCI Remove the Boc group with HCl then treat with HBr in tnfluoroacetic acid to cleave Phe Gly from the solid support... 

Phenylalanine- and Tyrosine-Derived Alkaloids. Carbohydrate metaboHsm leads via a seven-carbon sugar, ie, a heptulose, derivative to shikimic acid [138-59-0] (57), C H qO, which leads in turn to prephenic acid [126-49-8] (58), (43). 

For the separation of amino acids, the applicability of this principle has been explored. For the separation of racemic phenylalanine, an amphiphilic amino acid derivative, 1-5-cholesteryl glutamate (14) has been used as a chiral co-surfactant in micelles of the nonionic surfactant Serdox NNP 10. Copper(II) ions are added for the formation of ternary complexes between phenylalanine and the amino acid cosurfactant. The basis for the separation is the difference in stability between the ternary complexes formed with d- or 1-phenylalanine, respectively. The basic principle of this process is shown in Fig. 5-17 [72]. 

Similarly, the oxazoHdine (it,S)-147, obtained as a mixture of epimers at C2 from N,N-dibenzyl (it)-phenylalaninal and hl-benzyl (S)-valinol, reacted with Grignard reagents to form in situ the iminium ion 148, from which the diamino alcohols 149 were produced as a single diastereomer [71 ] (Scheme 23). On the other hand, when the oxazoHdine derived from the (S)-aldehyde was used, the diamino alcohol was obtained as a 70 30 mixture of diastereomers. Alhough the preparation of the primary 1,2-diamines was not explored in that paper, compoimds 149 would be the precursors of the syn 1,2-diamine... 

Tyrosine. Phenylalanine hydroxylase converts phenylalanine to tyrosine (Figure 28-10). Provided that the diet contains adequate nutritionally essential phenylalanine, tyrosine is nutritionally nonessential. But since the reaction is irreversible, dietary tyrosine cannot replace phenylalanine. Catalysis by this mixed-function oxygenase incorporates one atom of O2 into phenylalanine and reduces the other atom to water. Reducing power, provided as tetrahydrobiopterin, derives ultimately from NADPH. 

Selectivity studies with DTU indicated marked discrimination in the clathrate formation 23,45). As in other types of clathrates, the steric factor is important in differentiation between compounds of similar functionality but different shape. For example, DTU forms crystalline complexes with some alcohols (methanol, ethanol, propanol, 1-butanol) but not with others (2-butanol). It complexes the ethyl esters of N-acetyl derivatives of glycine, alanine, methionine and aspartic acid, but not of proline, serine, phenylalanine and glutamic acid. 

Rozwadowski et al.33 have shown for Schiff base being derivatives of L-phenylalanine and 2-hydroxynaphthaldehyde [16] that shielding of the H-8 and H-a signals relative to the chemical shifts of these positions for other amino acid Schiff bases was connected with the anisotropy of the aromatic ring of the phenylalanine. 

A similar reaction of A-toluenesulfonyl derivatives of (.S )-alanine, phenylalanine, and valine (188-190) with PhPCl2 gave 4-methyl, benzyl, and isopropyl derivatives of 2-phenyl-1-p-toluenesulfonyl-l, 3,2-oxazaphospholidin-5-one, 191-193 in high yields (Scheme 53) [84], The ratios of the (2.V,4.V)/(2/f,4.V) diastereomers (which were designated as cis/trans isomers) were 1 1, 2 1, and 10 1 for 191a,b, 192a,b, and... 

Figure 17.4 Ketone derivatives of phenylalanine and mannose can be fed to cells to incorporate the monomers into proteins and glycans. The resultant modifications can be probed using hydrazide-containing reagents.

Many secondary phenolic compounds are derived from the amino acids phenylalanine and tyrosine and therefore contain an aromatic ring and a three-carbon side chain (see Fig. 3.3). Phenylalanine is the primary substrate for phenylpropanoid synthesis in most higher vascular plants, with tyrosine being used to a lesser extent in some plants. Because of their common structure, compounds derived from these amino acids are collectively called phenylpropanoids. 

As early as 1905 Abderhalden (Al) isolated from the hydrolyzate of the nondiffusible fraction of human urine four amino acids, i.e., leucine, alanine, glycine, and glutamic acid, and detected two others phenylalanine and aspartic acid. Some amino acids derived from this fraction have been quantitatively determined by Albanese et al. (A3) who found in the amount of the nondiffusible fraction corresponding to one liter of urine as much as 32.8 mg tryptophan, 18.0 mg phenylalanine, 16.2 mg methionine, 15.2 mg cystine, 13.1 mg arginine, 6.7 mg histidine, and 3.9 mg tyrosine. 

Considerable amounts of glutamic acid, glycine, and alanine, as well as smaller quantities of aspartic acid, serine, threonine, basic amino acids, leucine, phenylalanine, and cystine have been demonstrated in a total hydrolyzate of the nondiffusible fraction by Boulanger et al. (BIO). Using Deacidite resin, they separated this material into two polypeptide fractions, acid and alkaline, and found that glutamic acid, aspartic acid, leucine, and certain cystine derivatives were the chief constituents of the former, whereas the latter contained considerable amounts of glycine, basic amino acids, and alanine. 

The enantioselective nitroaldol reaction of phe-nylalaninals 45 with nitromethane was also promoted with the N-anthracenylmethyl ammonium fluorides in the presence of potassium fluoride.1411 Interestingly, as shown in Scheme 16, the major product was the (2R,3S)-isomer 46a when N,N-dibenzyl-(S)-phenylalaninal and 12 (R=benzyl, X=F) were used while the (2S,3S)-isomer 46b was major when N-tert-butoxycarbonyl derivative 45b and 12 (R=allyl, X=Br) together with potassium fluoride were used. The nitroalcohols 46a and 46b were respectively converted to amprenavir 47a, a HIV protease inhibitor, and its diastereomer 47b. The... 

Synthesis of Substituted Derivatives of L-Phenylalanine and of other Non-natural L-Amino Acids Using Engineered Mutants of Phenylalanine Dehydrogenase... 

Racemic mixtures of underivatized amino acids N-alkyl- and N-aryl-substitued derivates of amino acids (phenylalanine and proline) on graphitic carbon 0.001 M Cu(acetate)2 aqueous solution 229, 230... 

Infants with classic phenylketonuria (PKU) are normal at birth but if untreated show slow development, severe mental retardation, autistic symptoms, and loss of motor control. Children may have pale skin and white-blonde hair. The neurotoxic effects relate to high levels of phenylalanine and not to the phenylketones from which the name of the disease derives. Infants are routinely screened a few days after birth for blood phenylalanine level. Treatment consists of a life-long semisynthetic diet restricted in phenylalanine (smalt quantities are necessary because it is an essential amino acid). Aspartame (N-aspartyl-phenylalanine methyl ester), which is widely used as an artificial sweetener, must be strictly avoided by phenyiketonurics. 

Tyrosine is structurally related to and derived from phenylalanine. It is the metabolic precursor to dopamine, an important neurotransmitter. Tyrosine is also the precursor to the hormones epinephrine and norepinephrine and to melanin, the pigment of skin. 

Some rather important indole derivatives influence our everyday lives. One of the most common ones is tryptophan, an indole-containing amino acid found in proteins (see Section 13.1). Only three of the protein amino acids are aromatic, the other two, phenylalanine and tyrosine being simple benzene systems (see Section 13.1). None of these aromatic amino acids is synthesized by animals and they must be obtained in the diet. Despite this, tryptophan is surprisingly central to animal metabolism. It is modified in the body by decarboxylation (see Box 15.3) and then hydroxylation to 5-hydroxytryptamine (5-HT, serotonin), which acts as a neurotransmitter in the central nervous system. 

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