A process of manufacturing a compound of formula or a salt thereof, wherein R 1 represents Ar 1, -CO-Ph, -CH 2 -( o -COR)Ph, -CH 2 -( o -NO 2)Ph or -CO-CO-NR 2, wherein Ar 1 represents phenyl or coumarin groups, optionally substituted by a group selected from nitro, alkoxy, halo, hydroxyl, amino, alkylamino, dialkylamino, alkyloxycarbonylalkyloxy, alkyloxyaryl, aryl, arylvinylyl, arylethynyl, cyano; Ph represents a phenyl group, optionally substituted by one or more group selected from alkoxy, halo, hydroxyl, alkyl, haloalkyl, haloalkoxy, amino, alkylamino, dialkylamino, alkyloxycarbonylalkyloxy, alkyloxyaryl, aryl, arylvinylyl, arylethynyl and cyano; and R represents aryl, alkyl or vinylcarboxy; wherein the aryl group is optionally substituted by one or more group selected from alkoxy, halo, hydroxyl, alkyl, haloalkyl, haloalkoxy, amino, alkylamino, dialkylamino, alkyloxycarbonylalkyloxy, alkyloxyaryl, aryl, arylvinylyl, arylethynyl and cyano; R 1' represents H, alkyl, haloalkyl, cyano, aryl; R 2 and R 3 represent each independently hydrogen, alkyl, carbamimidoyl; or R 2 and R 3 form together with the nitrogen atom to which they are attached an heterocyclic ring, preferably selected from pyrrolidinyl, piperidinyl, N-methyl-piperazinyl, morpholinyl, pyrrolyl; n is an integer ranging from 1 to 6, preferably n is 1, 2, 3 or 4, more preferably n is 1 or 2; comprising the following steps: a) performing a McMurry coupling between 4,4'-dihydroxybenzophenone and cyclohexanone to form intermediate b) performing a phenol monosubstitution on intermediate with caging halide wherein R 1 and R 1' are as defined in formula and X 1 represents halo, preferably X 1 represents Br or Cl, more preferably X 1 represents Br, to form intermediate wherein R 1 and R 1' are as defined in formula, wherein step b) is performed in the dark, in a solvent in which intermediate and caging halide are soluble and in which intermediate is not soluble; and c) alkylating in the dark the remaining phenol of intermediate with derivative wherein n, R 2 and R 3 are as defined in formula and X 2 represents halo or sulfonate, preferably X 2 represents Cl, Br, I, mesylate, triflate or tosylate, more preferably X 2 represents Cl, to afford compound of formula. R 1 represents Ar 1, -CO-Ph, -CH 2 -( o -COR)Ph, -CH 2 -( o -NO 2)Ph or -CO-CO-NR 2, wherein Ar 1 represents phenyl or coumarin groups, optionally substituted by a group selected from nitro, alkoxy, halo, hydroxyl, amino, alkylamino, dialkylamino, alkyloxycarbonylalkyloxy, alkyloxyaryl, aryl, arylvinylyl, arylethynyl, cyano; Ph represents a phenyl group, optionally substituted by one or more group selected from alkoxy, halo, hydroxyl, alkyl, haloalkyl, haloalkoxy, amino, alkylamino, dialkylamino, alkyloxycarbonylalkyloxy, alkyloxyaryl, aryl, arylvinylyl, arylethynyl and cyano; and R represents aryl, alkyl or vinylcarboxy; wherein the aryl group is optionally substituted by one or more group selected from alkoxy, halo, hydroxyl, alkyl, haloalkyl, haloalkoxy, amino, alkylamino, dialkylamino, alkyloxycarbonylalkyloxy, alkyloxyaryl, aryl, arylvinylyl, arylethynyl and cyano; R 1' represents H, alkyl, haloalkyl, cyano, aryl; R 2 and R 3 represent each independently hydrogen, alkyl, carbamimidoyl; or R 2 and R 3 form together with the nitrogen atom to which they are attached an heterocyclic ring, preferably selected from pyrrolidinyl, piperidinyl, N-methyl-piperazinyl, morpholinyl, pyrrolyl; n is an integer ranging from 1 to 6, preferably n is 1, 2, 3 or 4, more preferably n is 1 or 2; a) performing a McMurry coupling between 4,4'-dihydroxybenzophenone and cyclohexanone to form intermediate b) performing a phenol monosubstitution on intermediate with caging halide wherein R 1 and R 1' are as defined in formula and X 1 represents halo, preferably X 1 represents Br or Cl, more preferably X 1 represents Br, to form intermediate wherein R 1 and R 1' are as defined in formula, wherein step b) is performed in the dark, in a solvent in which intermediate and caging halide are soluble and in which intermediate is not soluble; and c) alkylating in the dark the remaining phenol of intermediate with derivative wherein n, R 2 and R 3 are as defined in formula and X 2 represents halo or sulfonate, preferably X 2 represents Cl, Br, I, mesylate, triflate or tosylate, more preferably X 2 represents Cl,