Imidazole → Methyl((1r,2r,3r,5s)-3-{[tert-butyl(dimethyl)silyl]oxy}-6-oxabicyclo[3.1.0]hex-2-yl)fluoroacetate

Participants

Reaction Conditions

Reaction Steps

To a solution of epoxy alcohol 3 (1.60 kg, 8.40 mol) and DMF (3.40 L) was added imidazole (1.26 kg, 18.5 mol) at 10° C. TBSCl (1.52 kg, 10.1 mol) was added to the reaction mixture while maintaining the batch temperature below 8° C. The resulting solution was stirred at 5° C. for 10 min, then allowed to warm to 20° C. over 30 min and stirred for 2 h at the same temperature. The consumption of the starting alcohol was monitored by GC, and the reaction mixture was diluted with cold toluene (17.0 L, 5° C.). The resulting mixture was washed with H2O (5.67 L), saturated aqueous NaHCO3 (5.67 L), H2O (5.67 L×2), and brine (5.67 L). Assay of the organic solution indicated 4. Concentration of the solution gave 4 as yellow liquid, which was used for the next step without further purification. Analytically pure sample was obtained by flash silica gel column chromatography (hexanes/MTBE) as colorless crystals: mp 28-30° C.; 1H NMR (400 MHz, CDCl3) δ 5.00 (dd, J=48.2, 3.5 Hz, 1H), 4.45 (m, 1H), 3.85 (s, 3H), 3.51 (m, 1H), 3.42 (m, 1H), 2.64-2.52 (dm, J=34.5 Hz, 1H), 2.14 (m, 1H), 1.91 (m, 1H), 0.88 (s, 9H), 0.054 (s, 3H), and 0.051 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 168.8 (d, J=24.1 Hz), 88.3 (d, J=186.1 Hz), 75.4 (d, J=1.6 Hz), 58.3, 57.2 (d, J=7.2 Hz), 52.8 (d, J=19.3 Hz), 52.7, 38.3, 25.9, 18.0, −4.5, and −4.7; 19F NMR (376 MHz, CDCl3) δ −199.9 (dd, J=48.2, 34.5 Hz); LRMS m/z 305 (M+1), 121 (base peak); [α]D25=−27 (c 1.0, CHCl3).

Provenance & Evidence