The present invention comprises aminoquinazoline compounds of the general formula I: wherein X is an unsubstituted or substituted phenyl, or is an unsubstituted or substituted 5 or 6 membered heteroaromatic ring. The compounds of the present invention are potent inhibitors of PTP1B. Accordingly, the invention also encompasses pharmaceutical compositions and methods of treating or preventing PTP-1B mediated diseases, including diabetes, obesity, and diabetes-related diseases.