Studies related to the total synthesis of the sesquiterpene core of the pyrrolobenzoxazine natural products CJ-12662 and CJ-12663

A highly effective procedure is reported to synthesize a substituted bicyclo[4.2.0]octenol derivative by regioselective cycloaddition of phenyl-1-propynyl sulfide with cyclohexenone followed by selective reduction of the ketone group and reductive elimination of phenylsulfonyl group. The strained cyclobutene ring was then engaged in a ring-opening/cross metathesis sequence in the presence of Hoveyda–Grubbs 2nd generation catalyst. The synthesis serves as a model study toward the synthesis of the sesquiterpene diol portion of the terpenoid pyrrolobenzoxazine alkaloids, CJ-12662 and CJ-12663.