Triethylamine → (3S,3aR,5R)-5-[(benzyloxy)methyl]-3-methyl-3,3a,4,5-tetrahydro-7H-pyrano[3,4-c][1,2]oxazole

Participants

Reaction Conditions

Reaction Steps

An aqueous solution of sodium hypochlorite (6.15% solution, 6.6 L) was slowly added to a solution of 2-{[(2R)-1-(benzyloxy)hex-4-en-2-yl]oxy}-N-hydroxyethanimine (C12) (660 g, 2.51 mol) and triethylamine (19 g, 0.19 mol) in dichloromethane (6.6 L) at 25° C. After completion of the addition, the reaction mixture was stirred at 25° C. for 30 minutes. The organic layer was washed with water (3×3 L), dried over sodium sulfate, filtered, and concentrated in vacuo. Purification via chromatography on silica gel (Eluent: ethyl acetate in petroleum ether) provided (3S,3aR,5R)-5-[(benzyloxy)methyl]-3-methyl-3,3a,4,5-tetrahydro-7H-pyrano[3,4-c][1,2]oxazole (C13) as a white solid. Yield: 90 g, 0.34 mol, 14%. The indicated relative stereochemistry of compound C13 was assigned based on NOE studies, which revealed interactions of the methine proton on carbon 3a with both the methine proton on carbon 5 and the protons of the methyl group on carbon 3. LCMS m/z 261.9 [M+H+]. 1H NMR (400 MHz, CDCl3) δ 7.24-7.39 (m, 5H), 4.69 (d, J=13.7 Hz, 1H), 4.57 (AB quartet, JAB=12.2 Hz, ΔνAB=13.8 Hz, 2H), 4.13-4.25 (m, 2H), 3.62-3.70 (m, 1H), 3.55 (dd, half of ABX pattern, J=10, 6 Hz, 1H), 3.47 (dd, half of ABX pattern, J=10, 4 Hz, 1H), 2.93 (br ddd, J=11, 11, 7 Hz, 1H), 2.11 (br dd, J=12.6, 6.8 Hz, 1H), 1.45-1.56 (m, 1H), 1.45 (d, J=6.2 Hz, 3H).

Provenance & Evidence