A mixture of (S)-5-tert-butoxy-4-(tert-butoxycarbonylamino)-5-oxopentanoic acid (3.03 g, 10 mmol) and methoxymethylamine HCl (1.17 g, 12 mmol) in HOBt (1.62 g, 12 mmol), EDC (2.3 g, 12 mmol) and NMM (3.3 mL, 30 mmol) was stirred at RT for 2 hr. The reaction was washed with 1N—HCl, NaHCO3 and sat. NaCl and dried over MgSO4. The solvent was removed to give 3.67 g of (S)-tert-butyl 3,11,11-trimethyl-4,9-dioxo-2,10-dioxa-3,8-diazadodecane-7-carboxylate, as a colorless oil. See, Syn. Lett. 2003, 10: 1411-1414.
