TLC: Rf = 0.55 [S2)], yield: 47% (Procedure B), m.p. 93˚C - 95˚C. IR ν (cm−1): 3450 (NH), 1694 (C=O ester), 1663 (C=O amide). 1H NMR (DMSO-d6, δ, ppm): 1.26 (t, J = 7.5 Hz, 3H, CH 2CH3), 3.6 - 3.63 (m, 4H, 2CH2, Pip-H), 3.67-3.7 (m, 4H, 2CH2, Pip-H), 4.1 (s, 2H, COCH2), 4.3 (q, J = 7.5 Hz, 2H, CH2CH3), 6.44 (d, J = 16 Hz, 1H, =CHCO), 6.98 (t, J = 3.5 Hz, 1H, Th- H4), 7.29 (d, J = 5 Hz, 1H, Th-H3), 7.47 (d, J = 16 Hz, 1H, CH=CH), 7.71 (d, J = 5 Hz, 1H, Th-H5), 8.43 (s, 1H, NH, exchangeable with D2O). Mass: m/z 352 ([M+1]+, 7%). Calcd. for C16H21N 3O4S (351.42). Calcd. C 54.68, H 6.02, N 11.96, S 9.12. Found: C, 54.56, H 5.96, N 12.96, S 9.00.