Route (8): The reaction of formula (Ia) where R8 is as defined earlier excluding hydrogen and all other symbols are as defined earlier and L3 is a leaving group such as halogen atom with an alcohol of general formula (Ib), where R7 is as defined earlier excluding hydrogen to produce a compound of the formula (I) may be carried out in the presence of solvents such as THF, DMF, DMSO, DME and the lik