[N:1]1([C:11]([O:13][C:14]([CH3:17])([CH3:16])[CH3:15])=[O:12])[CH2:6][CH2:5][NH:4][CH:3]([C:7]([O:9]C)=O)[CH2:2]1.[C:18]1([C@@H:24]2[CH2:26][C@H:25]2[N:27]=[C:28]=[O:29])[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1.CCN(C(C)C)C(C)C>C1(C)C=CC=CC=1>[O:9]=[C:7]1[CH:3]2[CH2:2][N:1]([C:11]([O:13][C:14]([CH3:17])([CH3:16])[CH3:15])=[O:12])[CH2:6][CH2:5][N:4]2[C:28](=[O:29])[N:27]1[C@@H:25]1[CH2:26][C@H:24]1[C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1To A3 in toluene (0.4M) was added dropwise trans-2-phenylcyclopropyl isocyanate (1.05 eq.). The mixture was stirred O/N at rt. DIPEA (1.5 eq.) was added and the mixture refluxed for 20 h. The organic phase was washed with phosphate buffer (2×200 mL, 0.75 M NaH2PO4, pH˜4.5) and the solvent removed under reduced pressure. The residue was purified by column chromatography on silica gel, eluting with 20-100% EtOAc/petroleum ether to give the title compound in 60% yield. MS (ES+) C20H25N3O4 requires 371, found: 394 (M+Na)+.
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