[Si:1]([O:8][CH2:9][C:10](=O)[CH2:11][C:12]1[C:13]([CH3:22])=[C:14]2[C:18](=[CH:19][CH:20]=1)[C:17](=[O:21])[O:16][CH2:15]2)([C:4]([CH3:7])([CH3:6])[CH3:5])([CH3:3])[CH3:2].[CH3:24][C:25]1[C:29](=[O:30])[O:28][CH2:27][C:26]=1[N:31]1[CH2:35][CH2:34][C:33]2([CH2:40][CH2:39][NH:38][CH2:37][CH2:36]2)[C:32]1=[O:41].C([BH3-])#N.[Na+]>CO.CC(C)[O-].[Ti+4].CC(C)[O-].CC(C)[O-].CC(C)[O-]>[Si:1]([O:8][CH2:9][CH:10]([N:38]1[CH2:39][CH2:40][C:33]2([C:32](=[O:41])[N:31]([C:26]3[CH2:27][O:28][C:29](=[O:30])[C:25]=3[CH3:24])[CH2:35][CH2:34]2)[CH2:36][CH2:37]1)[CH2:11][C:12]1[C:13]([CH3:22])=[C:14]2[C:18](=[CH:19][CH:20]=1)[C:17](=[O:21])[O:16][CH2:15]2)([C:4]([CH3:7])([CH3:6])[CH3:5])([CH3:3])[CH3:2]To a solution of 5-(3-((tert-butyldimethylsilyl)oxy)-2-oxopropyl)-4-methylisobenzofuran-1(3H)-one (0.50 g, 1.5 mmol) in methanol (20 mL) was added 2-(4-methyl-5-oxo-2,5-dihydrofuran-3-yl)-2,8-diazaspiro[4.5]decan-1-one (I-17) (0.45 g, 1.8 mmol) and titanium(IV) isopropoxide (2.10 g, 7.5 mmol). After stirring at for room temperature 48 h, sodium cyanoborohydride (190 mg, 3.0 mmol) was added and the reaction mixture was stirred at room temperature for 20 h. The reaction mixture was quenched with water (10 mL), and the resulting inorganic precipitate was filtered off and washed with methanol (50 mL). The filtrate was then concentrated and the crude product was dissolved in ethyl acetate, filtered to remove the remaining inorganic solids, and concentrated. The residue was purified by flash column chromatography (0-10% methanol in dichloromethane) to give the title compound. LC-MS (ESI, m/z): 569 [M+1]+.
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