The present invention provides compounds of formula (I): compositions comprising such compounds; the use of such compounds in therapy (for example in the treatment or prevention of a disease, disorder or condition ameliorated by inhibition of a dopamine transporter); and methods of treating patients with such compounds; wherein R1, R2, R3, R4, R9a, R9b, R9c, R9d, R9e, R9f, m, n, A, L and B are as defined herein.