tert-butyl (2S)-2-amino-3-(4-hydroxyphenyl)propanoate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: L-tyrosine tert-butyl ester (10.0 g) was acylated with 2,6-difluorobenzoyl chloride in a similar manner as described Example 1-(5) to give N-(2,6-difluorobenzoyl)-L-tyrosine tert-butyl ester (15.9 g). mp. 145-148° C.; IR (Nujol) 1728, 1638 cm−1; MS (APCI) m/z 395 (M+NH4), 378 (M+H).

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: L-tyrosine tert-butyl ester (10.0 g) was acylated with 2,6-difluorobenzoyl chloride in a similar manner as described Example 1-(5) to give N-(2,6-difluorobenzoyl)-L-tyrosine tert-butyl ester (15.9 g). mp. 145-148° C.; IR (Nujol) 1728, 1638 cm−1; MS (APCI) m/z 395 (M+NH4), 378 (M+H).

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: L-tyrosine tert-butyl ester (10.0 g) was acylated with 2,6-difluorobenzoyl chloride in a similar manner as described Example 1-(5) to give N-(2,6-difluorobenzoyl)-L-tyrosine tert-butyl ester (15.9 g). mp. 145-148° C.; IR (Nujol) 1728, 1638 cm−1; MS (APCI) m/z 395 (M+NH4), 378 (M+H).

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: L-tyrosine tert-butyl ester (10.0 g) was acylated with 2,6-difluorobenzoyl chloride in a similar manner as described Example 1-(5) to give N-(2,6-difluorobenzoyl)-L-tyrosine tert-butyl ester (15.9 g). mp. 145-148° C.; IR (Nujol) 1728, 1638 cm−1; MS (APCI) m/z 395 (M+NH4), 378 (M+H).

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 3,4-diethoxy-1-oxo-1,2,5-thiadiazole (1 g, 0.52 mmol) and L-tyrosine t-butyl ester (1.25 g, 0.52 mmol) in ethanol (25 mL) was stirred at room temperature for 60 hr. Solvent was removed under reduced pressure and the residue purified by flash column chromatography (silica, hexane:EtOAc 1:1 to give the title intermediate (1.75 g, 88%) Solvent was removed under reduced pressure the residue purified by flash column chromatography (silica, hexane:EtOAc 1:1

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 3,4-diethyloxy-1,1-dioxo-1,2,5-thiadiazole (400 mg, 1.94 mmol)and L-tyrosine t-butyl ester (1.25 g, 5.2 mmol) in ethanol (25 mL) was stirred at room temperature overnight. Solvent was removed under reduced pressure and the product used in further transformations without further purification (Yield 790 mg). Solvent was removed under reduced pressure the product used in further transformations without further purification (Yield 790 mg)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 3,4-diethyloxy-1,1-dioxo-1,2,5-thiadiazole (400 mg, 1.94 mmol)and L-tyrosine t-butyl ester (1.25 g, 5.2 mmol) in ethanol (25 mL) was stirred at room temperature overnight. Solvent was removed under reduced pressure and the product used in further transformations without further purification (Yield 790 mg). Solvent was removed under reduced pressure the product used in further transformations without further purification (Yield 790 mg)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 4-(N,N-di-n-hexylamino)-3-ethoxy-1,1-dioxo-1,2,5-thiadiazole (400 mg, 1.02 mmol) and L-tyrosine t-butyl ester (261 mg, 1.1 mmol) in EtOH (10 mL) was stirred at room temperature for 36 hrs. The solvent was removed under reduced pressure residue purified by flash column chromatography (silica, hexane:EtOAc 3:1 then 1:1) to give the title compound as a white waxy solid (400 mg, 73%). The solvent was removed under reduced pressure residue purified by flash column chromatography (silica, hexane:EtOAc 3:1

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a 0° C. suspension of L-tyrosine tert-butyl ester (Bachem, 1.0 eq) and sodium bicarbonate (2.0 eq) in a 1:1 mixture of THF and water was added slowly with stirring benzyl chloroformate (1.1 eq). After the addition, the mixture was stirred at 0° C. for 3 h and at room temperature for 24 h. The mixture was diluted with diethyl ether, and the aqueous layer was separated. The organic extracts were washed with saturated sodium chloride, treated with anhydrous magnesium sulfate, filtered, and evaporated to afford N-benzyloxycarbonyl-L-tyrosine tert-butyl ester of sufficient purity for immediate conversion of the tyrosine hydroxyl into a carbamate. After the addition the aqueous layer was separated The organic extracts were washed with saturated sodium chloride treated with anhydrous magnesium sulfate filtered evaporated

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a 0° C. suspension of L-tyrosine tert-butyl ester (Bachem, 1.0 eq) and sodium bicarbonate (2.0 eq) in a 1:1 mixture of THF and water was added slowly with stirring benzyl chloroformate (1.1 eq). After the addition, the mixture was stirred at 0° C. for 3 h and at room temperature for 24 h. The mixture was diluted with diethyl ether, and the aqueous layer was separated. The organic extracts were washed with saturated sodium chloride, treated with anhydrous magnesium sulfate, filtered, and evaporated to afford N-benzyloxycarbonyl-L-tyrosine tert-butyl ester of sufficient purity for immediate conversion of the tyrosine hydroxyl into a carbamate. After the addition the aqueous layer was separated The organic extracts were washed with saturated sodium chloride treated with anhydrous magnesium sulfate filtered evaporated

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 3,4-diethoxy-1-oxo-1,2,5-thiadiazole (1 g, 0.52 mmol) and L-tyrosine t-butyl ester (1.25 g, 0.52 mmol) in ethanol (25 mL) was stirred at room temperature for 60 hr. Solvent was removed under reduced pressure and the residue purified by flash column chromatography (silica, hexane:EtOAc 1:1 to give N-(4-ethoxy-1-oxo-1,2,5-thiadiazol-3-yl)-L-tyrosine tert-butyl ester (1.75 g, 88%). MS (+ESI, m/e) 382 (M+H)+. Solvent was removed under reduced pressure the residue purified by flash column chromatography (silica, hexane:EtOAc 1:1

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 3,4-diethoxy-1-oxo-1,2,5-thiadiazole (1 g, 0.52 mmol) and L-tyrosine t-butyl ester (1.25 g, 0.52 mmol) in ethanol (25 mL) was stirred at room temperature for 60 hr. Solvent was removed under reduced pressure and the residue purified by flash column chromatography (silica, hexane:EtOAc 1:1 to give N-(4-ethoxy-1-oxo-1,2,5-thiadiazol-3-yl)-L-tyrosine tert-butyl ester (1.75 g, 88%). MS (+ESI, m/e) 382 (M+H)+. Solvent was removed under reduced pressure the residue purified by flash column chromatography (silica, hexane:EtOAc 1:1