if I remember correctly, mephedrone is 4-methyl-methcathinone. It might be 4-methylcathinone, but I think it's the former.
some of the variants are valerones I think. less is known about them. and propriones too I think. the further away from the safe but illegal molecules you get, the more the potential side effects, typically. a side effect of the analogues acts are that people keep being pushed to more dangerous alternatives.
google is our friend - so I checked - yes I was right the first time.
http://en.wikipedia.org/wiki/Mephedrone