2,6-Lutidine → (R)-N-Allyloxyalanine benzyl ester

Participants

Reaction Steps

A solution of triflic anhydride (10.86 g, 38.5 mmol) in dry CH2Cl2 (20 mL) was added dropwise to a solution of benzyl (S)-lactate (1a) (6.31 g, 35 mmol) in dry CH2Cl2 (100 mL) with cooling (−68˜−72° C.) and stirring. After 5˜7 min, a solution of 2,6-lutidine (4.31 g, 40.3 mmol) in dry CH2Cl2 (15 mL) was added dropwise at the same temperature and the reaction mixture was stirred for 30 min at −68˜−72° C. A solution of O-allylhydroxylamine (4.55 g, 77 mmol) in dry CH2Cl2 (15 mL) was added dropwise to the prepared solution of the alkylating reagent with cooling (−68˜−72° C.) and stirring. The reaction mixture was stirred for 15 min at ca. −72° C. and then was allowed to warm up to RT. After stirring for 15 h at RT, the reaction mixture was thoroughly shaken with sat. aqueous NaHCO3 (200 mL) and dried over MgSO4. After removal of the solvent, the residue was purified by dry flash chromatography (Silica Gel 60H for TLC, 10% EtOAc-hexanes) to afford 8.20 g (99.6%) of the product 2a as a pale yellowish oil. 1H NMR (100 MHz) in CDCl3+1 drop of D2O (J, Hz): δ 1.28 (3H, d, 3J=7.1, MeCH), 3.82 (1H, q, 3J=7.1, MeCH), 4.22 (2H, dt, 3J=5.7, 4J=1.2, OCH2CH═CH2), 5.16-5.37 (2H, m, CH═CH2), 5.23 (2H, CH2Ph), 5.76-6.15 (1H, m, 3J=5.7, 3Jcis=9.9, 3Jtrans=17.1, CH═CH2), 7.38 (5H, Ph). 13C (100 MHz) in CDCl3: δ 14.81, 59.09, 66.63, 75.22, 117.53, 128.06, 128.24, 128.56, 134.37, 135.84, 174.01. IR (film), cm−1: 3264, 1740, 1456, 1208, 1170. Anal. Calcd for C13H17NO3: C, 66.4; H, 7.3; N, 5.95. Found: C, 66.3; H, 7.4; N, 6.15%.

Provenance & Evidence