A compound of the formula (I): wherein R1 is C1-C6 alkyl, amino, (C1-C6 alkyl)amino, di(C1-C6 alkyl)amino or a nitrogen-containing saturated heterocyclic; R2 and R3 are hydrogen or C1-C6 alkyl; Arom is phenyl, idenyl, napthyl, phenanthrenyl, furyl, thiolyl, pyrrolyl, azepinyl, pyrazolyl, imidazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, 1,2,3 oxadiazolyl, pyranyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl or quinolyl; A is C1-C6 alkylene; Ra is hydrogen, C1-C6 alkyl or C2-C6 alkenyl; E is a single bond, oxygen, sulfur or —NR4—, wherein R4 is hydrogen or C1-C7 alkanoyl; X1 and X2 are oxygen or sulfur; or a pharmacologically acceptable salt or ester thereof.