You cannot make any 4-piperidone from piperine (the 'active principle' of pepper).
What piperine is good for is the preparation of piperonal (unrelated to piperidone) and piperidine (cannot be used for piperidone synthesis either).
Hey Rhodium - thanks a lot, that nearly answers my question anyhow! :)
(seems i didn't use the FSE right somehow, looks like one should be able to find out the right route and starting point to 4-Piperidone ...)