N2-(tert-Butoxycarbonyl)-N1-((1S)-3-chloro-2-oxo-1-{[(3S)-2-oxopyrrolidin-3-yl]methyl}propyl)-l-norleucinamide
Following the procedure described for the preparation of N2-(tert-butoxycarbonyl)-N1-((1S)-3-chloro-2-oxo-1-{[(3S)-2-oxopyrrolidin-3-yl]methyl}propyl)-l-leucinamide but substituting Boc-NorLeu-OH and making noncritical variations provided a golden syrup. This material was purified by LC (100 g 230–400 SiO2, 2.5–3.5% methanol/chloroform) to afford 727 mg (42%) of the title compound as a light yellow foam. 1H NMR (DMSO-d6) δ 8.45 (d, J = 8 Hz, 1H), 7.62 (s, 1H), 7.00 (d, J = 8 Hz, 1H), 4.59 (d, J = 16 Hz, 1H), 4.53 (d, J = 16 foam in a 42% isolated yield. 1H Hz, 1H), 4.38 (m, 1H), 3.80 (m, 1H), 3.15 (m, 1H), 3.06 (m, 1H), 2.22 (m, 1H), 2.07 (m, 1H), 1.98 (m, 1H), 1.63–1.51 (m, 4H), 1.36 (m, 9H), 1.24 (m, 4H), 0.83 (t, J = 8 Hz, 3H); MS (ESI+) for C19H32ClN3O5m/z 418.1 (M + H)+.