Cl.[CH3:2][CH:3]1[CH2:8][CH2:7][CH2:6][NH:5][CH:4]1[C:9]([OH:11])=[O:10].Cl[C:13]([O:15][CH2:16][C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1)=[O:14].C1(C)C=CC=CC=1>[OH-].[Na+].C1COCC1>[CH2:16]([O:15][C:13]([N:5]1[CH2:6][CH2:7][CH2:8][CH:3]([CH3:2])[CH:4]1[C:9]([OH:11])=[O:10])=[O:14])[C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=13-Methylpiperidine-2-carboxylic acid hydrochloride (28.5 g, 31.6 mmol) was dissolved in (1:1) 2 M NaOH/THF (600 mL) and cooled to 0° C. Benzyl chloroformate (31.57 ml, 222 mmol) was then added dropwise and the reaction was stirred overnight. Toluene was then added and organic layer discarded to remove unreacted chloroformate. The aqueous layer was made acidic (pH=2) with conc. HCl and the product was extracted with EtOAc, dried (MgSO4), and concentrated in vacuo to give a crude residue which was used without further purification (41.6 g, 94.5%). 1H NMR (CDCl3, 400 MHz) δ 7.40-7.37 (m, 5H), 5.19 (m, 2H), 4.95-4.72 (m, 1H), 4.14-4.03 (m, 1H), 3.36-3.25 (m, 1H), 1.93-1.53 (m, 5H), 1.20-1.05 (m, 3H).
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