Claimed is a process for the manufacture of compounds of the following general formula (II): wherein R x represent a group selected from COOCH 2 CH 3 , SO 2 CH 3 , CONHCH 3 , and COCH 3 , comprising the step of reacting the compound of the following formula (±-13) with a compound of the general formula R x -X, wherein X represents a leaving group and wherein R x is as defined above. Also claimed is a process for the manufacture of pharmaceutical compositions comprising compounds of the following formula (II) or pharmaceutically acceptable salts or solvates thereof.
