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(1) To a mixture of <strong>[4089-07-0]L-<strong>[4089-07-0]tyrosine ethyl ester hydrochloride</strong></strong> (55.08 g) and NaHCO3 (22.52 g) in CH2Cl2/H2O (280 ml/280 ml) was added di-tert-butyl bicarbonate (56.82 g) portionwise. The mixture was stirred for 2 hours at room temperature and diluted with AcOEt. The organic layer was washed with H2O, dried (Na2SO4) and evaporated. The residue was recrystallized from a mixture of diethyl ether and hexane to yield N-(tert-butoxycarbonyl)-L-tyrosine ethyl ester (62.71 g). mp. 87-88° C.; MS (APCI) m/z 327 (M+NH4), 310 (M+H).
tert-butyl (2,4-dioxo-3-azaspiro[5,5]undecan-3-yl) carbonate[ No CAS ]
[ 4089-07-0 ]
[ 72594-77-5 ]
Yield
Reaction Conditions
Operation in experiment
84%
With triethylamine; In dichloromethane; at 38 - 40℃;
General procedure: L-Phenylalanine methyl ester hydrochloride (5.0 g, 23.2 mmol), triethyl amine (2.47 g, 24.4 mmol) and 2 (7.24 g, 24.4 mmol) were added to dichloromethane (50 mL) and stirred at reflux temp (38-40°C) for 5h. After completion of the reaction, filtered to remove salts and the filtrate was washed with 5percent KHSO4 (20 mL), water (25 mL), brine (25 mL), and dried over sodium sulfate. The solvent was evaporated under reduced pressure to obtain a pale yellow oil. The oil was purified by column chromatography (silica gel, ethyl acetate/ hexane, 8:2) to afford 5.96 g (92percent) Methyl (tert-butoxycarbonyl)-L-phenylalaninate as a colorless oil.
Chemistry
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