Compounds of formula (II) can be prepared by reaction of a compound of formula (V) with a compound of formula (V) via a Suzuki coupling reaction followed by deprotection of group R13 when R13 is not equal to H: in which X, Y and Z are as defined in formula (I) or are protected derivatives thereof, R13 is H or a suitable protecting group, for example benzyl, L1 is iodide, bromi