New 5-aminolevulinic acid prodrugs for use in photodynamic therapy and photodynamic diagnosis

There is provided a compound of Formula and salts thereof wherein R1 is an imine or an alkylated imine, said imine or alkylated imine comprising a linear or branched alkyl group of length C1 to C5; R2 are each independently (a) an unsubstituted or substituted linear or branched alkyl group of chain length C1-7; (b) an aryl substituted alkyl group, wherein said aryl group is substituted, (c) an alkoxy substituted alkyl group, wherein said alkoxy group is substituted by a methoxy group or an alkoxy group substituted with an alkoxy group; or (d) an H atom; wherein said substituents in (a) and (b) are selected from hydroxy, alkoxy, acyloxy, alkoxycarbonyloxy, amino, aryl, nitro, oxo and fluoro groups. R3 and R4 are linear or branched alkyl groups of length C1 to C6 constituting a ketal or a cyclic ketal. The compounds claimed may be used for the manufacture of a medicament.