A process is provided for removing one or more metals from liquids. Also provided is a process for the synthesis of aP2 inhibiting compounds having the formula (I) ##STR00001## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, HET, and X-Z are as described herein, which process comprising the step of removing one or more metals from a solution of the compound of formula I or an intermediate or precursor thereof. The processes for removing metal comprise the step of contacting the liquid with a solid extractant comprising a metal-binding functionality.