compounds having the structural formula i or a pharmaceutically acceptable salt thereof , wherein r is optionally substituted phenyl , cycloalkenyl , or heteroaryl ; x is alkylene or — cch 2 —; y is — nch 2 ch 2 n 3 )—, — och 2 ch 2 n —, — o —, — s —, — ch 2 s —, — 2 — nh —, or optionally substituted m and n are 2 - 3 , and q is nitrogen or optionally substituted carbon ; and z is optionally substituted phenyl , phenylalkyl or heteroaryl , diphenylmethyl , r 6 — c —, r 6 — so 2 —, r 6 — oc —, r 7 — n — c —, r 7 — n — c —, phenyl - ch —, or phenyl - c —; or when q is ch , phenylamino or pyridylamino ; or z and y together are substituted piperidinyl or substituted phenyl ; and r 2 , r 3 , r 6 , r 7 , and r 8 are as defined in the specification are disclosed , their use in the treatment of parkinson &# 39 ; s disease , alone or in combination with other agents for treating parkinson &# 39 ; s disease , and pharmaceutical compositions comprising them ; also disclosed are a processes for preparing intermediates useful for preparing compounds of formula i .