D-Phenylalanine → D-Phenylalanine 1,1-dimethylethyl ester

To a solution of D-phenylalanine (1.651 g, 10.0 mmol) in tert-butyl acetate (20 mL) at 0° C., was slowly added HClO4 (0.85 mL, 15 mmol). The reaction mixture was stirred at room temperature for 12 h then washed with H2O (25 mL) and 1.0 M HCl solution (15 mL). The resultant aqueous solution was adjusted to pH 9 by addition of 10% K2CO3 solution, and then extracted with dichloromethane (3×10 mL). The combined organic phases were dried with anhydrous Na2SO4, filtered and concentrated to give an oil. This was purified by flash chromatography on silica gel, using a grading of ethyl acetate/hexane ((1:5) to (2:5)), to give A1 as a colorless oil; (2.020 g, 89.3%). Spectral data were in accordance with those published. [α]D25: −39.5 (c=0.33, CHCl3); 1H-NMR (300 MHz, CDCl3): δ 7.35-7.29 (m, 2H), 7.27-7.22 (m, 3H), 3.63 (dd, J=6.0, 9.0 Hz, 1H), 3.09-3.02 (m, 1H), 2.89-2.82 (m, 2H), 1.47 (s, 2H), 1.44 (s, 9H); 13C NMR (300 MHz, CDCl3): δ 174.34, 137.57, 129.39, 128.41, 126.65, 81.12, 56.33, 41.29, 28.00; LRMS (ESI): calcd for: C13H19NO2 [M+H]+=222.1, obsd [M+H]+=222.1, [M+Na]+=244.1, obsd [M+Na]+=244.1.

1. customat 0° C.
2. washthen washed with H2O (25 mL) and 1.0 M HCl solution (15 mL)
3. additionThe resultant aqueous solution was adjusted to pH 9 by addition of 10% K2CO3 solution
4. extractionextracted with dichloromethane (3×10 mL)
5. dry with materialThe combined organic phases were dried with anhydrous Na2SO4
6. filtrationfiltered
7. concentrationconcentrated
8. customto give an oil
9. customThis was purified by flash chromatography on silica gel

ORD record

ord-f22bab61f6ba49b89c6b98c4776495d2

Source dataset

uspto-grants-2016_08

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09409880B2