Tyrosine 0-methyl ether

Synthesis of Enantiomerically Pure (3-Amino Acid from 2-tert-Butyl-l-carbomethoxy-2,3-dihydro-4(1 H)-pyrimidinone (S)- 3-Tyrosine-0-methyl Ether. 

Danishefsky and Cain examined several amino acids for asymmetric aldolization of trione (118 equation 141). With L-proline, the hydrindenedione (119) was obtained in only 27% ee. However, L-pheny-lalanine was more effective, giving (119) with 85% ee. Other amino acids (tyrosine 0-methyl ether. 

In polar solvents, the structure of the acridine 13 involves some zwitterionic character 13 a [Eq. (7)] and the interior of the cleft becomes an intensely polar microenvironment. On the periphery of the molecule a heavy lipophilic coating is provided by the hydrocarbon skeleton and methyl groups. A third domain, the large, flat aromatic surface is exposed by the acridine spacer unit. This unusual combination of ionic, hydrophobic and stacking opportunities endows these molecules with the ability to interact with the zwitterionic forms of amino acids which exist at neutral pH 24). For example, the acridine diacids can extract zwitterionic phenylalanine from water into chloroform, andNMR evidence indicates the formation of 2 1 complexes 39 such as were previously described for other P-phenyl-ethylammonium salts. Similar behavior is seen with tryptophan 40 and tyrosine methyl ether 41. The structures lacking well-placed aromatics such as leucine or methionine are not extracted to measureable degrees under these conditions. 

Recognition of amino acids has been attempted more frequently with receptors that are likewise zwitterionic in nature (compare 35). Some early studies include the transport of phenylalanine by a merocyanine dye through a liposomal bilayer [53]. Rebek s dicarboxylate-complexing cleft 9 (see Sect. 2) turned out to be a selective (though achiral) binder of trypthophane, phenylalanine, and tyrosine methyl ether [54]. A reasonable structure for a phenylalanine complex of 2 1 stoichiometry, as deduced from NMR studies, is schematically represented in formula 39 [55]. 

The toxic Japanese gastropod Turbo marmorata contains the two toxins, turbotoxins A (1983) and B (1984), isolated as bis-trifluoroacetates (1824, 1825). The turbotoxins A and B show LD99 = 1.0 and 4.0 mg kg 1 in mice. The simple iodinated ammonium salt 1985 is also found in this animal (1826). The red alga Halopytis incurvus contains the simple brominated phenols 1986 and 1987, which were isolated as the methyl esters and methyl ethers (1827). These presumed degradation products of tyrosine are related to earlier reported brominated metabolites (1). 

The tyrosine phenolic hydroxyl function was readily methylated to form a methyl ether under aqueous conditions at pH 10 with the proteins... 

The synthesis starts from the A-Boc-tyrosine methyl ester, which was O-benzylated, since the prenyl ether required in the target compound is not compatible with the conditions required for the preparation of the hydoxylamine or the hydrogenation of the isoxazolidine intermediate (Scheme 40). Following cleavage of the A-Boc, the resulting primary amine was treated with anisaldehyde, and after oxidation with m-CPBA... 

Use. When the reactivity of 4-bromoacetamidoestrone methyl ether was examined, n-cysteine, L-methionine, L-histidine, L-lysine, n-trypto-phan, L-tyrosine, and A-acetylhistidine were shown to be alkylated by the steroid derivative, but alanine was not. Assay revealed that 4-bromoacetamidoestrone methyl ether is a substrate for estradiol 17 -dehydro-genase and thus binds at the active site. It has a K of 0.14 mAf. Radioactive 4-bromoacetamidoestrone methyl ether (0.2 mAf) was used to... 

The Dim ester was developed for the protection of the carboxyl function during peptide synthesis. It is prepared by transesterification of amino acid methyl esters with 2-(hydroxymethyl)-l,3-dithiane and Al(/-PrO)3 (reflux, 4 h, 75°, 12 torr, 75% yield). It is removed by oxidation [H2O2, (NH4)2Mo04 pH 8, H2O, 60 min, 83% yield]. Since it must be removed by oxidation it is not compatible with.sulfur-containing amino acids such as cysteine and methionine. Its suitability for other, easily oxidized amino acids (e.g., tyrosine and tryptophan) must also be questioned. It is stable to CF3CO2H and HCl/ether. - ... 

Cimbura and Kofoed (50),mentioned earlier, used GLC to separate amphetamine and methamphetamine after acetylation with acetic anhydride in methanol. Derivatives were extracted using diethyl ether and chromatographed op columns of either 3% OV-17, OV-1, or SE-30. Column temperature was 160°C. They also reported the chromatographic determination of acetylated morphine on 3% SE-30, OV-1, or OV-17 at temperatures of 220°C. Cruickshank et al.(21) separated 21 amino acids as their trifluoroacetylated methyl esters. The column was 5% neopentyl glycol succinate on Gas Chrom P. Column temperatures were both isothermal and programmed 65°C for 20 min at 1.5°C/min then 2°C/min until 42.5 min then 4°C/min until 60 min then isothermal until about 75 min (see Figure 12.2). Chang et al. (19), used BSA/pyridine to form the TMS derivatives of levodopa, methyldopa, tyrosine. 

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