Cl[C:2]1[N:3]=[CH:4][C:5]2[C:10]([CH3:12])([CH3:11])[O:9][C:8]([CH3:14])([CH3:13])[C:6]=2[N:7]=1.[C:15]([O:19][C:20]([N:22]1[CH2:27][CH2:26][CH:25]([NH2:28])[CH2:24][CH2:23]1)=[O:21])([CH3:18])([CH3:17])[CH3:16]>CN(C=O)C>[C:15]([O:19][C:20]([N:22]1[CH2:27][CH2:26][CH:25]([NH:28][C:2]2[N:3]=[CH:4][C:5]3[C:10]([CH3:12])([CH3:11])[O:9][C:8]([CH3:14])([CH3:13])[C:6]=3[N:7]=2)[CH2:24][CH2:23]1)=[O:21])([CH3:18])([CH3:16])[CH3:17]A mixture of 2-chloro-5,5,7,7-tetramethyl-5,7-dihydro-furo[3,4-d]pyrimidine (1.60 g, 7.52 mmol, 1.0 equiv; intermediate B1) and 4-amino-piperidine-1-carboxylic acid tert-butyl ester (1.81 g, 9.03 mmol, 1.2 equiv; commercially available) in anhydrous DMF (6 mL) was heated by microwave irradiation to 150° C. for 30 min. The organic phase was concentrated under reduced pressure and the residue purified with column chromatography on silica eluting with a gradient of heptane/ethyl acetate (10:1)→ethyl acetate providing 1.26 g (45%) of the title compound. MS (ISP): 377.4 [M+H]+.
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