A Compound of structural formula: wherein: X denotes a link -O- or -CH 2 -; and R denotes -H or an linear or branched C 1-4 alkyl group; R 1 denotes - n-(CH 2) m -, wherein in independent way n=1 or 2 and m=0, 1, 2, 3 and 4, -NH-CO-NH- or -NH-C -NH-, wherein the moiety - is characterized by any of the chemical moieties -(T-1), -(T-2), -(T-2) or -(T-4) and corresponding substituents, as further defined; R 2 denotes -OH, -NH 2, -O-CH-(C 2 H 5) 2, -NH-CO-CH 3, -NH-CO-CH 2 -OH, -NH-CO-C 2 H 5, -NH-C NH 2; wherein optionally only one terminal hydrogen of any of those preceeding moieties R 2 may be substituted by a moiety - or - or by a moiety of another known antiviral, antibacterial or antiprotozoarian compound, with the proviso that no hydrogen of R 3 shall be substituted by any moiety; and R 3 denotes -OH, -NH 2, -NH-CO-CH 3, -NH-CO-CH 2 -OH, -NH-CO-C 2 H 5, or -NH-C NH 2; wherein optionally only one terminal hydrogen of any of those preceeding moieties R 3 may be substituted by a moiety - or- or by a moiety of another known antiviral antibacterial or antiprotozoarian compound, with the proviso that no hydrogen of R 2 shall be substituted by any moieties; and R 4 denotes independently from R 1, the moiety -CHOH-CHOH-CH 2 -OH, -, -CHOH-CH 2 - or -CH 2 -, wherein the moiety -, characterized by any of the chemical moieties -(W-1), -(W-2) and corresponding substituents, as further defined; and their linear or branched C 1-4 carboxy mono or poly esters, addition salts, solvates, resolved enantiomers and purified diastereoisomers; the moiety - of R 1, R 2, R 3 independently from - of R 4, denotes the structure -(T-1): • wherein: - R 5 denotes -H, -CH 3, -C 2 H 5, -CH-(C 2 H 5) 2; and - R 6 denotes -NH-CO-CH3, -NH-CO-C 2 H 5; and - R 7 denotes -O-CH-(CH 3) 2, -O-CH-(C 2 H 5) 2. the moiety - of R 1, R 2, R 3 independently from - of R 4, denotes the structure -(T-2): the moiety - of R 1, R 2, R 3 independently from - of R 4, denotes the structure -(T-3): the moiety - of R 1, R 2, R 3 independently from - of R 4, denotes the structure -(T-4): • wherein: - Z denotes -H, -CH-(C 2 H 5) 2, -CO-(CH 2) 6 -CH 3 4 - of R 2, R 3, R 4, independently from moiety - of R 1, denotes the structure -(W-1): • wherein: - R 8 denotes the linking function: - NH-, -CH 2 -NH-, -CH(CH 3)-NH-, - NH-CH(CH 3)-NH-, -C(CH 3) 2 -CH 2 -NH-, - NH-CO-CH 2 -O-CH 2 -CH 2 -NH- or by or by - R 9 denotes -H, -CH 3 or -C 2 H 5; and - R 10 denotes -H, -CH 3 or -C 2 H 5. - of R 2, R 3, R 4, independently from moiety - of R 1, denotes the structure -(W-2): • wherein: - R 11 denotes the linking function: - NH-, -CO-NH- or -C -NH-; X denotes a link -O- or -CH 2 -; and R denotes -H or an linear or branched C 1-4 alkyl group; R 1 denotes - n-(CH 2) m -, wherein in independent way n=1 or 2 and m=0, 1, 2, 3 and 4, -NH-CO-NH- or -NH-C -NH-, wherein the moiety - is characterized by any of the chemical moieties -(T-1), -(T-2), -(T-2) or -(T-4) and corresponding substituents, as further defined; R 2 denotes -OH, -NH 2, -O-CH-(C 2 H 5) 2, -NH-CO-CH 3, -NH-CO-CH 2 -OH, -NH-CO-C 2 H 5, -NH-C NH 2; wherein optionally only one terminal hydrogen of any of those preceeding moieties R 2 may be substituted by a moiety - or - or by a moiety of another known antiviral, antibacterial or antiprotozoarian compound, with the proviso that no hydrogen of R 3 shall be substituted by any moiety; and R 3 denotes -OH, -NH 2, -NH-CO-CH 3, -NH-CO-CH 2 -OH, -NH-CO-C 2 H 5, or -NH-C NH 2; wherein optionally only one terminal hydrogen of any of those preceeding moieties R 3 may be substituted by a moiety - or- or by a moiety of another known antiviral antibacterial or antiprotozoarian compound, with the proviso that no hydrogen of R 2 shall be substituted by any moieties; and R 4 denotes independently from R 1, the moiety -CHOH-CHOH-CH 2 -OH, -, -CHOH-CH 2 - or -CH 2 -, wherein the moiety -, characterized by any of the chemical moieties -(W-1), -(W-2) and corresponding substituents, as further defined; • wherein: - R 5 denotes -H, -CH 3, -C 2 H 5, -CH-(C 2 H 5) 2; and - R 6 denotes -NH-CO-CH3, -NH-CO-C 2 H 5; and - R 7 denotes -O-CH-(CH 3) 2, -O-CH-(C 2 H 5) 2. - R 5 denotes -H, -CH 3, -C 2 H 5, -CH-(C 2 H 5) 2; and - R 6 denotes -NH-CO-CH3, -NH-CO-C 2 H 5; and - R 7 denotes -O-CH-(CH 3) 2, -O-CH-(C 2 H 5) 2. • wherein: - Z denotes -H, -CH-(C 2 H 5) 2, -CO-(CH 2) 6 -CH 3 4 - Z denotes -H, -CH-(C 2 H 5) 2, -CO-(CH 2) 6 -CH 3 4 • wherein: - R 8 denotes the linking function: - NH-, -CH 2 -NH-, -CH(CH 3)-NH-, - NH-CH(CH 3)-NH-, -C(CH 3) 2 -CH 2 -NH-, - NH-CO-CH 2 -O-CH 2 -CH 2 -NH- or by or by - R 9 denotes -H, -CH 3 or -C 2 H 5; and - R 10 denotes -H, -CH 3 or -C 2 H 5. - R 8 denotes the linking function: - NH-, -CH 2 -NH-, -CH(CH 3)-NH-, - NH-CH(CH 3)-NH-, -C(CH 3) 2 -CH 2 -NH-, - NH-CO-CH 2 -O-CH 2 -CH 2 -NH- or by or by - NH-, -CH 2 -NH-, -CH(CH 3)-NH-, - NH-CH(CH 3)-NH-, -C(CH 3) 2 -CH 2 -NH-, - NH-CO-CH 2 -O-CH 2 -CH 2 -NH- or by or by - R 9 denotes -H, -CH 3 or -C 2 H 5; and - R 10 denotes -H, -CH 3 or -C 2 H 5. • wherein: - R 11 denotes the linking function: - NH-, -CO-NH- or -C -NH-; - R 11 denotes the linking function: - NH-, -CO-NH- or -C -NH-; - NH-, -CO-NH- or -C -NH-;