One synthetic advantage of olefin metathesis is that the catalyst tolerates the presence o...

One synthetic advantage of olefin metathesis is that the catalyst tolerates the presence of a variety of functional groups in the reactant. In a synthesis of the antiinfluenza drug Tamiflu (Section 23.25), for example, ring-closing metathesis was used to prepare the highly functionalized cyclohexene derivative shown in the equation. What was the reactant?