Sodium Sulfite → (S)-2-t-butoxycarbonylamino-3-(tetrahydro-pyran-2-yl)-propionic acid

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[(S)-2-Hydroxy-1-(tetrahydro-pyran-2-ylmethyl)-ethyl]-carbamic acid t-butyl ester (843 mg, 3.64 mmol) was dissolved in acetonitrile (18 mL) and phosphate buffer (pH=7, 14 mL). Then 1-oxyl-2,2,6,6-tetramethylpiperidine (40 mg) was added. The mixture was warmed to 35° C. To this clear solution was added a solution of sodium chlorite (832 mg) in water (4 mL) and catalytic amount of bleach (1 mL of 5.25% sodium hypochlorite solution was diluted with water to 20 mL, 1.80 mL of the diluted solution was used). The mixture was stirred at 35° C. for 1.5 hr. Then a second portion of sodium chlorite (832 mg) in water (4 mL) and catalytic amount of diluted bleach was added over 2 h. The mixture was stirred for 1 h and then diluted with water (25 mL) and treated with sodium sulfite solution. The mixture was extracted with methyl t-butyl ether. The aqueous layer was acidified with 1N aqueous hydrochloric acid and extracted with methyl t-butyl ether. The organic layer was washed with saturated sodium chloride solution and solvents were evaporated to afford (S)-2-t-butoxycarbonylamino-3-(tetrahydro-pyran-2-yl)-propionic acid (707 mg, 71%) as an oil: [α]D=+23.8 (chloroform); LR-ES-MS m/z calculated for C13H23NO5 [M]+ 273, observed [M+H]+ 274; 1H NMR (300 MHz, CDCl3) δ ppm 1.30-1.70 (m, 5H), 1.46 (s, 9H), 1.76-2.13 (m, 3H), 3.31-3.69 (m, 2H), 3.99, 4.07 (2×d, J=11.2 Hz, 1H), 4.35 (br. s., 1H), 5.52, 5.88 (2×br. s., 1H).

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