Synthesis of a bicyclo[2.2.2]octane from benzoic acid
Supposed that the synthesis does involve a Diels-Alder reaction, it is nowhere written that it is the last step in the sequence.

Take another look at your product and imagine a $\ce{C=C}$ double bond somewhere. Does it now look more like a Diels-Alder product? The $\ce{C=C}$ can be turned to $\ce{C-C}$ using... (You figure that out).

Work your path back from here and try to identify diene and dienophile.


Don't look until you've figured out the diene ;)


   Convert acid to ester, 2 x $\ce{MeMgBr}$, Diels-Alder reaction with vinylmethyl ether, hydrogenate double bond. You didn't cheat, did you? ;)