Never heard of it, but "legal mdpv" is probably not accurate. In the US all mdpv is legal (not an analog of anything schedule 1 or 2), in the UK all mdpv is illegal.
Probably an mdpv analog, something like pentylone, but it's anyones quess which one. Someone posted a link to a chart of what's in legal highs stuff a couple days ago, probably the best answer you'll get will be there.