A process for preparing a compound of formula (I) wherein n is 0 or 1, which process comprises: a) reacting a compound of formula (II) wherein n is 0 or 1, with a compound of formula (III) wherein X is selected from -NHSO 2 Me and -NOz and Z is selected from -OH, chlorine, bromine, linear or branched (C 1 -C 6 )alkoxy, aryloxy, arylalkoxy, (C 1 -C 6 )alkylcarbonyloxy, arylcarbonyloxy and aryl(C 1 -C 6 )alkylcarbonyloxy to obtain a compound of formula (I) wherein n is 0 or 1 or a compound of formula (IV) wherein n has the above reported meanings; and, when a compound of formula (IV) is obtained in step (a): b) reducing it to a corresponding compound of formula (V) wherein n is 0 or 1, and reacting it with methanesulfonyl halide to obtain a compound of formula (I) wherein n has the above reported meanings; and wherein the compound of formula (II) is obtained according to step (c3) by: c3) reacting an intermediate of formula B" with an intermediate of formula D wherein R is a linear or branched (C 1 -C 6 ) alkyl group or a arylalkyl group and n has the above reported meanings, to obtain directly a compound of formula (VII) and subsequently enantioselectively reducing it to obtain a compound of formula (II) wherein n has the above reported meanings; and wherein all of the compounds of formula (I), (II), (IV), (V) or (VII) wherein n is 1 can be obtained by oxidizing the corresponding compounds wherein n is 0. a) reacting a compound of formula (II) wherein n is 0 or 1, with a compound of formula (III) wherein X is selected from -NHSO 2 Me and -NOz and Z is selected from -OH, chlorine, bromine, linear or branched (C 1 -C 6 )alkoxy, aryloxy, arylalkoxy, (C 1 -C 6 )alkylcarbonyloxy, arylcarbonyloxy and aryl(C 1 -C 6 )alkylcarbonyloxy to obtain a compound of formula (I) wherein n is 0 or 1 or a compound of formula (IV) wherein n has the above reported meanings; and, when a compound of formula (IV) is obtained in step (a): b) reducing it to a corresponding compound of formula (V) wherein n is 0 or 1, and reacting it with methanesulfonyl halide to obtain a compound of formula (I) wherein n has the above reported meanings; and wherein the compound of formula (II) is obtained according to step (c3) by: c3) reacting an intermediate of formula B" with an intermediate of formula D wherein R is a linear or branched (C 1 -C 6 ) alkyl group or a arylalkyl group and n has the above reported meanings, to obtain directly a compound of formula (VII) and subsequently enantioselectively reducing it to obtain a compound of formula (II) wherein n has the above reported meanings; and wherein all of the compounds of formula (I), (II), (IV), (V) or (VII) wherein n is 1 can be obtained by oxidizing the corresponding compounds wherein n is 0. b) reducing it to a corresponding compound of formula (V) wherein n is 0 or 1, and reacting it with methanesulfonyl halide to obtain a compound of formula (I) wherein n has the above reported meanings; and wherein the compound of formula (II) is obtained according to step (c3) by: wherein n is 0 or 1, and reacting it with methanesulfonyl halide to obtain a compound of formula (I) wherein n has the above reported meanings; and wherein the compound of formula (II) is obtained according to step (c3) by: c3) reacting an intermediate of formula B" with an intermediate of formula D wherein R is a linear or branched (C 1 -C 6 ) alkyl group or a arylalkyl group and n has the above reported meanings, to obtain directly a compound of formula (VII) and subsequently enantioselectively reducing it to obtain a compound of formula (II) wherein n has the above reported meanings; and wherein all of the compounds of formula (I), (II), (IV), (V) or (VII) wherein n is 1 can be obtained by oxidizing the corresponding compounds wherein n is 0. <EOS>