A compound of formula (I) or a salt, ester, amide or prodrug thereof; where X is O, or S, S(O), S(O).sub.2 or NR.sup.6 where R.sup.6 is hydrogen of C.sub.1-6alkyl; R.sup.5 is an optionally substituted 6-membered aromatic ring containing at least one nitrogen atom, and R.sup.1, R.sup.2, R.sup.3, R.sup.4 are independently selected from halogeno, cyano, nitro, C.sub.1-3alkylsulphanyl, --N(OH)R.sup.7-- (wherein R.sup.7 is hydrogen, or C.sub.1-3alkyl), or R.sup.9X.sup.1-- (wherein X.sup.1 represents a direct bond, --O--, --CH.sub.2--, --OC(O), --C(O)--, --S--, --SO--, --SO.sub.2--, --NR.sup.10C(O)--, --C(O)NR.sup.11--, --SO.sub.2NR.sup.12--, --NR.sup.13SO.sub.2-- or NR.sup.14-- (wherein R.sup.10, R.sup.11, R.sup.12, R.sup.13 and R.sup.14 each independently represents hydrogen, C.sub.1-3alkyl or C.sub.1-3alkoxyC.sub.2-3alkyl), and R.sup.9 is hydrogen, optionally substituted hydrocarbyl, optionally substituted heterocyclyl or optionally substituted alkoxy; provided that at least one of R.sup.2 or R.sup.3 is other than hydrogen. These compounds inhibit aurora 2 kinase and are useful in the preparation of medicaments for the treatment of proliferative disease such as cancer.