The present invention relates to compounds of the formula I: wherein: ring C is an 8, 9, 10, 12 or 13-membered bicyclic or tricyclic moiety which moiety may be saturated or unsaturated, which may be aromatic or non-aromatic, and which optionally may contain 1-3 heteroatoms selected independently from O, N and S; is —O— —NH— or —S—; is 0, 1, 2, 3, 4 or 5; is 0, 1, 2 or 3; and R2 and R1 are as defined herein; and salts thereof; their use in the manufacture of a medicament for use in the production of an antiangiogenic and/or vascular permeability reducing effect in warm-blooded animals; processes for the preparation of such compounds; pharmaceutical compositions containing a compound of formula I or a pharmaceutically acceptable salt thereof and methods of treating disease states involving angiogenesis by administering a compound of formula I or a pharmaceutically acceptable salt thereof. The compounds of formula I inhibit the effects of VEGF, a property of value in the treatment of a number of disease states including cancer and rheumatoid arthritis.