GENERAL STEPS: L-(+)-p-hydroxyphenylglycine (1.00 g, 5.98 mmol) and sodium bicarbonate (2.50 g, 29.11 mmol) were dissolved in a solvent mixture of 1,4-dioxane (20 mL) and water (20 mL) at 0 °C. Di-tert-butyl dicarbonate (1.40 g, 6.58 mmol) was added slowly, followed by warming the reaction mixture to room temperature and stirring for 18 hours. Upon completion of the reaction, the organic solvent was removed by evaporation under reduced pressure and the residue was subjected to liquid-liquid partitioning with ethyl acetate (300 mL) and 0.5 M aqueous hydrochloric acid (50 mL). The organic phase was separated, washed sequentially with 0.5 M aqueous hydrochloric acid, water and saturated saline, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford the white solid product (S)-2-((tert-butoxycarbonyl)amino)-2-(4-hydroxyphenyl)acetic acid (1.6 g, quantitative yield). The product was characterized by 1H NMR (400 MHz, CDCl3): δ 8.80 (broad single peak, 1H), 7.12 (double peak, 2H), 6.62 (double peak, 2H), 5.80 (double peak, 1H), 5.00 (double peak, 1H), 1.22 (single peak, 9H). Mass spectrometry (EI) analysis was consistent with the molecular formula C11H17NO5: [M-H]- m/z 266.
