A compound selected from the group consisting of 14-O-[((Guanidino-imino-(C 1)alkyl)-phenylsulfanyl)-acetyl]-mutilins, 14-O-[((Ureido-imino-(C 1)alkyl)-phenylsulfanyl)-acetyl]-mutilins, 14-O-[((Thioureido-imino-(C 1)alkyl)-phenylsulfanyl)-acetyl]-mutilins, 14-O-[((Isothioureido-imino-(C 1))alkyl)-phenylsulfanyl)-acetyl]-mutilins, wherein the phenyl ring is optionally further substituted by up to four groups independently selected from halogen, (C 1 - 6)alkyl, aryl, aryl(C 1-6)-alkyl, (C 1-6)alkoxy, (C 1-6)alkoxy(C 1-6)alkyl, halo(C 1-6)alkyl, aryl-(C 1-6)alkoxy, hydroxy, nitro, cyano, azido, acyloxy, carbamoyl, mono-or di-N-(C 1-6)alkylcarbamoyl, (C 1-6)-a1koxycarbonyl, aryloxycarbonyl, ureido, guanidino, (C 1-6)alkylguanidino, amidino, (C 1-6)alkylamidino, sulphonylamino, aminosulphonyl, (C 1-6)alkylthio, (C 1-6)-alkylsulphinyl, (C 1 - 6) alkylsulphonyl, heterocyclyl, heteroaryl, heterocyclyl(C 1-6)alkyl and heteroaryl(C 1-6)alkyl, or two adjacent ring carbon atoms may be linked by a (C 3-5) alkylene chain, to form a carbocyclic ring; the compounds 14-O-[3-{[(2-Pyrrolidin-1-yl-ethoxyimino)-methyl]-phenylsulfanyl}-acetyl]-mutilin and 14-O-[{3-[(2-Morpholin-4-yl-ethoxyimino)-methyl]-phenylsulfanyl}-acetyl]-mutilin, a compound of formula wherein n is 0, Y is NR 3, R 3 is a group of formula or together with a corresponding anion, X is oxygen, sulfur, NH or NR 7, R 4, R 5, R 6, R 7 are hydrogen, linear or branched C 1-6 alkyl or C 3-8 cycloalkyl, and R 8 is C 1-4 alkyl., and a compound of formula, wherein n is 0, Y is NR 3, X is NR 7, R 3 is and R 4 and R 7 together with the nitrogen atoms to which they are attached form a 5 to 7 membered heterocyclic ring containing at least 2 nitrogen atoms, whereas R 5 and R 6 are as defined above, or and R 5 and R 6 together with the nitrogen atoms to which they are attached form a 5 to 7 membered heterocyclic ring containing at least 2 nitrogen atoms, whereas R 4 and R 7 are as defined above, or and R 4 and R 5 together with the nitrogen atoms to which they are attached form a 5 to 7 membered heterocyclic ring containing one or more nitrogen atoms, whereas R 6 and R 7 as defined above. wherein n is 0, Y is NR 3, R 3 is a group of formula or together with a corresponding anion, X is oxygen, sulfur, NH or NR 7, R 4, R 5, R 6, R 7 are hydrogen, linear or branched C 1-6 alkyl or C 3-8 cycloalkyl, and R 8 is C 1-4 alkyl., and a compound of formula, wherein n is 0, Y is NR 3, X is NR 7, R 3 is and R 4 and R 7 together with the nitrogen atoms to which they are attached form a 5 to 7 membered heterocyclic ring containing at least 2 nitrogen atoms, whereas R 5 and R 6 are as defined above, or and R 5 and R 6 together with the nitrogen atoms to which they are attached form a 5 to 7 membered heterocyclic ring containing at least 2 nitrogen atoms, whereas R 4 and R 7 are as defined above, or and R 4 and R 5 together with the nitrogen atoms to which they are attached form a 5 to 7 membered heterocyclic ring containing one or more nitrogen atoms, whereas R 6 and R 7 as defined above. X is oxygen, sulfur, NH or NR 7, R 4, R 5, R 6, R 7 are hydrogen, linear or branched C 1-6 alkyl or C 3-8 cycloalkyl, and R 8 is C 1-4 alkyl., and a compound of formula, wherein n is 0, Y is NR 3, X is NR 7, R 3 is and R 4 and R 7 together with the nitrogen atoms to which they are attached form a 5 to 7 membered heterocyclic ring containing at least 2 nitrogen atoms, whereas R 5 and R 6 are as defined above, or and R 5 and R 6 together with the nitrogen atoms to which they are attached form a 5 to 7 membered heterocyclic ring containing at least 2 nitrogen atoms, whereas R 4 and R 7 are as defined above, or and R 4 and R 5 together with the nitrogen atoms to which they are attached form a 5 to 7 membered heterocyclic ring containing one or more nitrogen atoms, whereas R 6 and R 7 as defined above.