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 benzylamide from Example 3a (100 mg, 0.31 mmol) in toluene (20 mL) was refluxed in the presence of p-TsOH.H2O (1.8 mg, 0.0093 mmol, 0.03 eq) for 24 h. After removal of the solvent, the residue was purified by a silica gel chromatography to yield 50 mg (53%) of title compound as a white solid: mp 124-127° C., 1H NMR (300 MHz, CDCl3) δ 7.01-7.35 (m, 10H), 6.84 (br s, 1H), 5.60 (s, 1H), 5.01 (d, J=15.7 Hz, 1H), 4.85 (d, J=15.7 Hz, 1H), 4.76 (s, 1H), 4.49-4.52 (m, 1H), 3.36 (dd, J=3.7, 13.6 Hz, 1H), 3.12 (dd, J=7.7, 13.6 Hz, 1H); HRMS (EI): m/z 306.1369 (M+) (calcd for C19H18N2O2: 306.1368). 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 purified by a silica gel chromatography