Abstract: A compound, or a solvate or a salt thereof, of formula (I): wherein R is linear or branched alkyl; R1 represents hydrogen or up to four optional substituents selected from the list consisting of: C1-6 alkyl, C1-6 alkenyl, aryl, C1-6 alkoxy, hydroxy, halogen, nitro, cyano, carboxy, carboxamido, sulphonamido, C1-6 alkoxycarbonyl, trifluoromethyl, acyloxy, phthalimido, amino or mono- and di-C1-6 alkylamino; R2 represents a moiety —(CH2)n—NY1Y2 wherein n is an integer in the range of from 1 to 9, Y1 and Y2 are independently selected from hydrogen; C1-6-alkyl; C1-6 alkyl substituted with hydroxy, C1-6 alkylamino or bis (C1-6 alkyl) amino; C1-6-alkenyl; aryl or aryl-C1-6-alkyl or Y1 and Y2 together with the nitrogen atom to which they are attached represent an optionally substituted N-linked single or fused ring heterocyclic group; R3 is branched or linear C1-6 alkyl, C3-7 cycloalkyl, C4-7 cycloalkylalkyl, optionally substituted aryl, or an optionally substituted single or fused rin