CH
2Cl
2 was added to a solution of epoxide 49 (0.00687 mol) via a
molecular sieve at 0
oC and stirred for an hour. BF
3 and diethyl ether (0.0206 mol each) were added to the solution, and the reaction was warmed to room temperature after twenty minutes. An additional 0.0206 mol of BF
3 and diethyl ether were added and the reaction was stirred for one hour. The reaction was
quenched with sodium bicarbonate and extracted with ethyl acetate. The organic layer was dried with MgSO
4, gravity-filtered, blown down, and purified with
preparative TLC.