[CH:1]([C:3]1[N:8]=[C:7]([C:9]([OH:11])=[O:10])[CH:6]=[CH:5][CH:4]=1)=O.[NH:12]1[CH2:17][CH2:16][CH2:15][CH2:14][CH2:13]1.C(O)(=O)C.C(O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+]>ClCCl>[N:12]1([CH2:1][C:3]2[N:8]=[C:7]([C:9]([OH:11])=[O:10])[CH:6]=[CH:5][CH:4]=2)[CH2:17][CH2:16][CH2:15][CH2:14][CH2:13]1
To a solution of 6-formyl-2-pyridinecarboxylic acid (available from Chemstep Product List, 250 mg, 1.65 mmol) in dichloromethane (5.8 ml) was added piperidine (0.428 ml, 4.33 mmol) and acetic acid (0.083 ml). The mixture was stirred at room temperature for 30 mins when sodium triacetoxyborohydride (459 mg, 2.17 mmol) was added and the mixture stirred for 45 mins. The mixture was loaded onto an aminopropyl cartridge (5 g) pre-eluted with dichloromethane. The cartridge was eluted with dichloromethane and methanol, and fractions containing product were combined and blown to dryness under a stream of nitrogen. The crude product was taken up in ethyl acetate (25 ml) and washed with sodium hydroxide solution (2M, 3×25 ml). The aqueous layer was acidified to pH6 using hydrochloric acid (5M) and concentrated under vacuum to approximately 25 ml. The solution was loaded onto an Oasis cartridge (6 g), which had been pre-eluted with methanol (1 volume) followed by water (1 volume). The cartridge was eluted with water (1 volume) followed by methanol. Fractions containing product were combined and dried to give the title compound (376 mg).
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