You would get ketones/epoxides using the oxone procedure on these molecules, but they would not be suitable for production of MDP2P - the side chain would be too long.
That's what I was afraid of. I was clinging to a glimmer of hope that the oxidation method was somehow selective to that first double carbon bond in piperic acid, just as some oxidation methods seem selective with respect to the alpha carbon. Piperine --> piperonal is not difficult at all, but I was hoping to save a step or two.
On a side note, though, the forensic paper by Carlson on your (Rhodium's) website seems to indicate that amines with extended carbon chains are good candidates for novel psychoactive compounds. Would any ketones produced by the oxidation of pieprine be candidates for these types of compounds?