反应详情

Using a Dean-Stark trap whose trap part was filled with molecular sieves 3A, a solution of N-2-oxo-propanoyl-L-phenylalanine amide from Example 1a (100 mg, 0.427 mmol) in toluene (20 mL) was refluxed in the presence of p-TsOH.H2O (4.37 mg, 0.023 mmol, 0.05 eq) for 18 h. After removal of the solvent, the residue was triturated in ether to obtain 89 mg (96%) of the title compound as a white solid: mp 175-177° C. (decomp); 1H NMR (300 MHz, DMSO-d6) δ 10.36 (s, 1H), 8.41 (s, 1H), 7.24-7.11 (m, 5H), 4.90 (s, 1H), 4.50 (s, 1H), 4.40-4.37 (m, 1H), 3.15 (dd, J=3.8, 13.5 Hz, 1H), 2.91 (dd, J=5.0, 13.5 Hz, 1H); HRMS (EI): m/z 216.0891(M+) (calcd for C12H12N2O2: 216.0899). Enantiomeric excess was determined to be >99% using chiral HPLC with a CHIRALCEL OD column.

1. customAfter removal of the solvent
2. customthe residue was triturated in ether