[CH3:1][O:2][C:3]([N:5](P(OC)(OC)=O)[CH:6]([CH3:10])[C:7]([O-:9])=[O:8])=[O:4].[CH3:17]N(C)C(N(C)C)=N.[O:25]1[CH2:30][CH2:29]C(=O)[CH2:27][CH2:26]1>O1CCCC1>[CH3:17][O:9][C:7](=[O:8])[C:6]([NH:5][C:3]([O:2][CH3:1])=[O:4])=[C:10]1[CH2:29][CH2:30][O:25][CH2:26][CH2:27]1A solution of N-methoxycarbonyl-2-methyl-(dimethylphosphono)glycinate (1.45 g, 5.68 mmol) in tetrahydrofuran (22 mL) was cooled to −78° C. 1,1,3,3-Tetramethylguanidine (0.680 mL, 5.42 mmol) was added and the resulting solution was stirred at −78° C. for 30 minutes. Tetrahydropyran-4-one (0.500 mL, 5.42 mmol) was added and the reaction was stirred at −78° C. for 1 hour. The ice bath was removed and the reaction was allowed to warm to room temperature overnight. In the morning, the reaction was diluted with ethyl acetate. The organics were washed with 1N aqueous HCl and brine, dried (MgSO4) and concentrated. The crude residue was purified by flash chromatography to yield methoxycarbonylamino-(tetrahydropyran-4-ylidene)-acetic acid methyl ester. 1H-NMR: 400 MHz, (CDCl3) δ: 5.94 (br s, 1H), 3.80-3.74 (m, 7H), 3.71 (s, 3H), 2.95-2.91 (m, 2H), 2.45-2.41 (m, 2H) ppm.
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