[CH2:1]([C:3]1[S:4][CH:5]=[C:6]([C:8]([N:10]2[CH2:15][C:14]3([CH2:20][CH2:19][N:18](C(OC(C)(C)C)=O)[CH2:17][CH2:16]3)[O:13][CH2:12][CH2:11]2)=[O:9])[N:7]=1)[CH3:2].Cl.CC(OC)(C)C>CC(O)C>[CH2:1]([C:3]1[S:4][CH:5]=[C:6]([C:8]([N:10]2[CH2:15][C:14]3([CH2:20][CH2:19][NH:18][CH2:17][CH2:16]3)[O:13][CH2:12][CH2:11]2)=[O:9])[N:7]=1)[CH3:2]To a solution of tert-butyl 4-(2-ethylthiazole-4-carbonyl)-1-oxa-4,9-diazaspiro[5.5]undecane-9-carboxylate (limiting reagent) (step a) in iPrOH (3 volumes) was added hydrogen chloride (2 molar equivalents of a 5-6N solution in iPrOH). The reaction mixture was heated and stirred at 49° C. (internal) for 18 hr before being cooled to 22° C. TBME (4.3 volumes) was added and the suspension was stirred at 22° C. for 3 days. The solid was collected by filtration, washed with TBME (3.5 volumes) and air dried for 2 days to give an off white solid. Yield 95% of theoretical.
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