Tyrosine methyl ester

Solution-phase enantioselective synthesis of 437 and 438 thus achieved was also translated into solid-phase synthesis <2002TL8981>. The oxazolidinone 441 prepared from L-tyrosine methyl ester via 440 was attached to Merrifield resin to produce 442. Resin-bound 442 was converted to 443 (Scheme 98). 

I vnmetiial Proved me. 1 1 llieiiliculion ul l- inoc-tyrosine methyl ester with a di.ilknwben/v I alcohol linker 117u ... 

Table 12.7 Yields of a-chymotrypsin-catalyzed peptide synthesis in water and ice using maleoyl-L-tyrosine methyl ester as acyl donor and various peptides, amino acid amides, and amino acids as nucleophiles (Schuster, 1990).

In order to find a synthetic route to diphenyl thioether derivatives of peptides and amino acids, the reaction of iodinated aryl amino acid, such as monoiodo (O-methyl) Boc-tyrosine methyl ester (214) with Boc-protected / -mercaptophenylalanine methyl ester (215) (R=Me), or the free acid (215, R = H) was studied in liquid ammonia, 90% yield of 216 from 215, R = Me were obtained (equation 149)281. 

Preparation of Boc-cyclohexylglycine-3-hydroxyl-tyrosine methyl ester... 

A solution of Boc-cyclohexylgylcine monohydrate (24.00 mmol) in 50 ml CH2C12 was treated with 4-methylmorpholine (26.0 mmol), then cooled to -10°C and treated with 3.5 ml isobutyl chloroformate. A white suspension was stirred until the temperature rose to 5°C. In a separate beaker 3-hydroxyl-tyrosine methyl ester hydrochloride salt (26.5 mmol) dissolved in 30 ml DMF was treated with 4-methylmorpholine (26.0 mmol) and stirred 15 minutes at ambient temperature. This mixture was added to the aforementioned mixture, then stirred 1 hour at ambient temperature, and then diluted with 100 ml 1M HC1. The aqueous layer was extracted three times with 200 ml EtOAc, then washed with 100 ml apiece 1M HC1, 1M NaOH, and brine, dried with Na2S04, and concentrated. The residue was purified by chromatography with silica gel using EtOAc/hexanes, 3 7, and the product isolated in 53% yield as a colorless foam. 

Similarly, the norbelladine derivative 489, prepared from L-tyrosine methyl ester and isovaniiine, was oxidized with PhI(OCOCF3)2 in trifiuoroethanol (TFE) at —40°C to afford in 64% yield an intramolecular coupled product 490. This is known as the key... 

The pyrimido-pteridine N-oxide (168) is well known as an electron acceptor and oxygen atom transfer agent. Its use for the hydroxylation of phenols has now been described.Ultra-violet light irradiation of (168) in acetonitrile solution allows conversion of phenol to a mixture of catecol and hydroquinone, cresol to 4-methylcatecol, tyrosine methyl ester to dopa methyl ester (169), and the pain killer acetaminophen (170) to (171). The reaction is initiated by light induced electron transfer from the phenol to the... 

Condensation of MTX with tyrosine methyl ester in aqueous pyridine in the presence of EDC hydrochloride was used [350] to prepare the y-peptide (VIII.232), along with the corresponding less polar a-peptide, from which it... 

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... 

Lipophilic prodrugs can also be derived from a carboxylic function, the most commonly used derivatives being carboxylic esters. Simple esters of aliphatic alcohols are attractive as they are cheap to prepare, chemically stable, and yield harmless hydrolysis products." Typical representatives of such prodrugs are tyrosine methyl ester," levodopa ethyl ester," nipecotic acid ethyl ester," enala-prilat ethyl ester," " " trandolapril," y-aminobutyric acid cetyl ester" " and methotrexate cetyl ester." ... 

We also completed the total synthesis of the unnatural discorhabdin A, (—)-discorhabdin A, starting from the o-tyrosine methyl ester by the same route as described for (+)-discorhabdin A (Scheme 32). 

Chiral intermediates for the synthesis of (-)-anisomycin (1) and (+)-anisomycin (anti-1) (153), (R)-2-(p-methoxyphenyl)methyl-2,5-dihydro-pyrrole (142) and its (S)-isomer (+)-187, have been efficiently synthesized from D-tyrosine and L-tyrosine, respectively (Scheme 20) [28]. D-tyrosine was converted to 0-methyl D-tyrosine methyl ester (182) [72-75] which was treated with di-tert-butyl dicarbonate to protect the amino group. Subsequent reduction of the ester group with sodium borohydride in the presence of lithium chloride furnished the alcohol 183. Swern oxidation of 183 followed by chain extension with the anion derived from bis(2,2,2-trifluoroethyl)(ethoxycarbonylmethyl)-phosphonate afforded (Z)-Q ,/0-unsaturated ester (184), which was used immediately without purification to avoid or minimize any possible racemization of the chiral center. Reduction of the ester group of 184 with diisobutylaluminium hydride afforded the alcohol 185 which after mesylation followed by intramolecular cyclization gave the desired 2,5-dihydropyrrole derivative 186. Removal of the tert-butyloxycarbonyl group was achieved by treatment with trifuoroacetic acid to give (-)-142 in 62% overall yield from 182. The (S)-2,5-dihydropyrrole (-l-)-187 was also prepared in the same manner starting from L-tyrosine. Since (-l-)-187 had been transformed into (-l-)-anisomycin (anti-1) (153), (-)-142 could also be transformed to the (-)-anisomycin (1) [26,66]. 

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