Either this is a compound I have never heard of, or you have horribly misspelled the compound.
Are you sure you are not referring to, "N-methyl-b-methylphenylethylamine"? I am sure you are, as the compound you have spelled, as far as I know, does not and cannot exist.
At any rate, the compound I think you are referring to is a phenethylamine (PEA) analogue or some manner of another, and almost reads like the beta-analogue of methamphetamine. Amphetamine is stated as alpha-methylphenethylamine, and methamphetamine is N-amphetamine, or alternatively, I believe, as N-methyl-alpha (A)-methylphenethylamine.
As for what the beta and alpha analogues share or do not share, that is beyond my knowledge. It would obviously be a sympathomimetic, with central stimulant properties, though.