NMR 6 3.10 (d, J= 6.6 Hz, 2H), 3.49 (t, J= 6.9 Hz, 1H), 3.77, 3.84 (AB, J= 14.5 Hz,

2H), 4.05 (dd, J= 5.2, 1.8 Hz, 1H), 4.12 (d, J= 5.0 Hz, 1H), 4.29, 4.65 (AB, J= 15.3 Hz,

2H), 7.02-7.15 (m, 3H), 7.16-7.27 (m, 6H); 13C NMR 6 30.0, 44.8, 52.4, 60.4, 68.4,

126.3, 126.6, 127.0, 127.5, 127.6, 128.7, 129.2, 133.8, 134.4, 135.6, 172.3. Anal. Calcd

for Ci8H18N20: C, 77.67; H, 6.52; N, 10.06. Found: C, 77.50; H, 6.83; N, 10.09.

3.4.6 General Procedure for the Preparation of 2,3,5-Trisubstituted-tetrahydro-4H-
imidazol-4-ones 3.16a-c.

 A mixture of a-amino-amide 3.10a-c (2.0 mmol), benzaldehyde (0.27 g, 2 mmol)

and p-TsOH (0.4 mmol) in CH3OH (15 mL) with anhydrous Na2SO4 (3.0 g) was stirred

refluxing for 12 hours. After evaporation of CH3OH under reduced pressure, the reaction

mixture was diluted with EtOAc. The organic phase was washed with 2 M NaOH, water,

brine, and dried over anhyd K2CO3. After removal of solvent in vacuo, the residue was

purified by column chromatography with hexanes/EtOAc (6:4) as an eluent to give trans-

3.16a and cis-3.16'a, and trans-3.16b,c.

 (2R,5S)-5-Benzyl-3-(4-methylphenyl)-2-phenyltetrahydro-4H-imidazol-4-one

(3.16a): yellowish microcrystals; yield, 38%; mp 106-107 OC; [a]25D= -52.5 (c 1.86,

CHC13); 1H NMR 6 1.70 (br s, 1H), 2.24 (s, 3H), 3.09-3.21(m, 2H), 4.13 (t, J= 5.5 Hz,

1H), 5.55 (s, 1H), 7.03, 7.11 (AB, J= 8.5 Hz, 4H), 7.22-7.32 (m, 10H); 13C NMR 6 20.8,

38.0, 60.2, 77.1, 122.0, 126.4, 126.8, 128.5, 128.8, 128.9, 129.4, 129.8, 134.2, 135.1,

137.3, 139.4, 173.7. Anal. Calcd for C23H22N20: C, 80.67; H, 6.48; N, 8.18. Found: C,

80.39; H, 6.51; N, 7.94.

 (2S,5S)-5-Benzyl-3-(4-methylphenyl)-2-phenyltetrahydro-4H-imidazol-4-one

(3.16'a): yellowish microcrystals; yield, 31%; mp 97-98 OC; [a]25D = -29.8 (c 1.58,