Reaction Steps
The compound was prepared from 33 and ethyl 4-aminobenzoate in a similar manner as described for preparation of 34. Chromatography on silica gel (7:3 hexanes/ethyl (Rf 0.20) afforded 35 as a brown solid in 72% yield. 1H NMR (400 MHz, CD3OD) δ 1.35 (9H, s, C(CH3), 1.35 (3H, t, J 6.8 Hz, CH2CH3), 2.63 (1H, dd, J 8.6, 14.6 Hz, H—CHCO), 2.77 (1H, dd, J 6.2, 14.6 Hz, H—CHCO), 3.35-3.40 (1H, m, CH2CHCH2), 4.31 (2H, q, J 7.2 Hz, CH2CH3), 7.24 (2H, d, J 8.8 Hz, 2×Ar—H), 7.28 (2H, d, J 8.8 Hz, 2×Ar—H), 7.57 (2H, d, J 8.4 Hz, 2×Ar—H), 7.91 (2H, d, J 9.2 Hz, 2×Ar—H). 13C NMR (400 MHz, CDCl3) δ 14.56 (s) (CH2CH3), 28.56 (s) (C(CH3)3), 40.92 (s) (CH2CO), 42.77 (s) (CH2CHCH2), 45.97 (s) (CH2NH), 61.04 (s) (C(CH3)3), 80.56 (s) (CH2CH3), 119.07 (s) (2×CH, Ar), 125.90 (s) (C, Ar), 129.08 (s) (2×CH, Ar), 129.17 (s) (2×CH, Ar), 130.90 (s) (2×CH, Ar), 133.17 (s) (C, Ar), 140.35 (s) (C, Ar), 142.65 (s) (C, Ar), 157.54 (s) (C═O), 166.47 (s) (C═O), 170.32 (s) (C═O). νmax (pure sample)/(cm−1)), 3353 (md), 1685 (st) (C═O), 1685 (st) (C═O), 1661 (st) (C═O), 1524 (st), 1273 (st), 1249 (st), 1188 (st), 769 (md).
