Reaction Steps
A solution of diethyl (((2 S,4S,5R,6R)-4,5-bis(benzyloxy)-6-((benzyloxy)methyl)-3-oxotetrahydro-2H-pyran-2-yl)methyl)phosphonate (1.3 g, 2.23 mmol, 1.0 equiv) in THF/MeOH (42 mL, 1:1) was treated with a buffer solution (17.68 mL) prepared with 15 g of AcONa.3H2O and 7.5 g of NH2OH.HCl. The pH was then adjusted to 4.5 by dropwise addition of acetic acid. After 1 hour, the mixture was extracted with DCM (3×30 mL), and the organic layer was washed sequentially with water (50 mL), saturated aqueous sodium bicarbonate solution (75 mL) and finally with water to neutrality. The organic layer was dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The product thus obtained was purified by silica gel chromatography, eluting with 60% EtOAc in hexane to give diethyl (((2S,4R,5S,6R)-4,5-bis(benzyloxy)-6-((benzyloxy)methyl)-3-(hydroxyimino)tetrahydro-2H-pyran-2-yl)methyl)phosphonate (0.98 g, 74%) as a mixture of E and Z isomers as a white solid. NMR data refers to the more abundant isomer. 1H NMR (400 MHz, DMSO-d6) δ 11.36 (d, J=1.1 Hz, 1H), 7.39-7.25 (m, 13H), 7.21 (dd, J=7.6, 2.0 Hz, 2H), 5.21 (td, J=10.6, 3.2 Hz, 1H), 4.73 (d, J=12.0 Hz, 1H), 4.64 (d, J=11.5 Hz, 1H), 4.57-4.47 (m, 4H), 4.40 (d, J=6.6 Hz, 1H), 4.04-3.91 (m, 5H), 3.71 (t, J=6.0 Hz, 1H), 3.60 (dd, J=10.1, 4.9 Hz, 1H), 3.53 (dd, J=10.2, 4.7 Hz, 1H), 2.70-2.53 (m, 1H), 2.11 (ddd, J=19.4, 15.7, 3.8 Hz, 1H), 1.19 (qd, J=7.1, 1.1 Hz, 6H). ESI (M+1) 598.0; calc for C32H40NO8P 597.3.
