S(O)(O)(=O)=O.[CH3:6][N:7](O)[C:8]([NH2:10])=[NH:9].[Na].[C:13]([O:17][C:18]([N:20]1[CH2:25][CH2:24][CH:23]=[C:22]([C:26]([O:28]C)=O)[CH2:21]1)=[O:19])([CH3:16])([CH3:15])[CH3:14].CC(C)([O-])C.[K+]>C(O)C.O>[C:13]([O:17][C:18]([N:20]1[CH2:25][CH2:24][CH:23]=[C:22]([C:26]2[O:28][N:10]=[C:8]([NH:7][CH3:6])[N:9]=2)[CH2:21]1)=[O:19])([CH3:16])([CH3:15])[CH3:14]N-Methyl-hydroxyguanidine sulphate (17.0 g, 0.061 mol) was stirred with 4A molecular sieves (20 g) in ethanol (80 mL) under a nitrogen atmosphere for 2 hours. Sodium (2.8 g, 0.122 mol) was added in portions then the mixture was stirred at 50° C. for 1 hour. A solution of methyl 1-t-butyloxycarbonyl-1,2,5,6-tetrahydropyridine-3-carboxylate (3.0 g, 0.012 mol) in ethanol (40 mL) was added and the reaction mixture was stirred whilst heating under reflux for 4 hours. The mixture was cooled, filtered, evaporated to dryness. The residue was dissolved in tetrahydrofuran (40 mL), treated with potassium t-butoxide (1.35 g, 0.012 mol) and stirred for 3 hours. Water (50 mL) was added and the mixture extracted with dichloromethane (5×50 mL). The combined organics were dried (sodium sulphate) then evaporated to dryness to give a yellow gum which was purified by column chromatography on silica using dichloromethane/methanol (80:1) afford the product as a pale yellow gum (1.10 g, 33%). (HRMS, Found: M+, 280.1530, C13H20N4O3 requires M, 280.1535). (Found: C, 54.70; H, 7.29; N, 18.91. C13H20N4O3 requires C, 55.70; H, 7.19, N, 19.99%).
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