Tyrosine 0-methyl ether syntheses

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

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... 

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. - ... 

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