C[Al](C)C.[NH2:5][C:6]1[CH:13]=[CH:12][C:9]([C:10]#[N:11])=[CH:8][N:7]=1.[Si:14]([O:21][CH:22]1[CH2:25][N:24]([CH2:26][C@H:27]([OH:32])[C:28](OC)=[O:29])[CH2:23]1)([C:17]([CH3:20])([CH3:19])[CH3:18])([CH3:16])[CH3:15]>C1(C)C=CC=CC=1>[Si:14]([O:21][CH:22]1[CH2:25][N:24]([CH2:26][C@H:27]([OH:32])[C:28]([NH:5][C:6]2[CH:13]=[CH:12][C:9]([C:10]#[N:11])=[CH:8][N:7]=2)=[O:29])[CH2:23]1)([C:17]([CH3:20])([CH3:19])[CH3:18])([CH3:16])[CH3:15]Trimethylaluminium (7.95 mL, 15.89 mmol) was added to 6-aminonicotinonitrile (1.646 g, 13.82 mmol) in toluene (50 mL) cooled to 0° C. under nitrogen. The resulting solution was stirred at 0° C. for 10 minutes. (S)-Methyl 3-(3-(tert-butyldimethylsilyloxy)azetidin-1-yl)-2-hydroxypropanoate (Intermediate AD3) (4.0 g, 13.82 mmol) in toluene (20 mL) was added and the resulting solution was allowed to warm to room temperature and then heated at 60° C. for 3 hours. The mixture was cooled to ˜10° C. and quenched by the addition of 20% Rochelle salt solution. It was then diluted with EtOAc (50 mL) and stirred for 2 hours. The organic phase was separated, washed with water and brine, dried (MgSO4), filtered and evaporated. The residue was purified by flash chromatography on silica with EtOAc as eluent to afford the product containing some 6-aminonicotinonitrile (4.1 g). This was used without further purification.
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