Compounds of formula (XIII) may be prepared by coupling a compound of formula (VI) as defined above, or a precursor thereof (wherein one or more of the substituents R1, R2 or R3 is a group which is convertible to the desired group R1, R2, or R3) with a compound of formula (VIII) as shown above wherein R4, R5, m, and n are as defined for the compound of formula (XIII) and L1 is a leaving group as d