Compounds of formula (I-1): wherein R 1 represents H, a straight or branched (C 1 -C 6)alkyl group or a -(CH 2) m -R 2 group with R 2 selected from the group comprising hydrogen, halogen, OH, N 3, NH 2, epoxy groups, leaving groups selected from halogen and sulfonyl group and carbonyl groups and m is an integer from 0 to 5, n is an integer from 0 to 5, X and Y independently of each other represent hydrogen, halogen or a straight or branched (C 1 -C 6)alkyl group or an hydroxyethyl group, and R' and R" independently of each other: (a) represent a group selected from the group comprising (i) an oxymethylcarbonyl group of formula wherein R 1 and R' 1 are independently of each other hydrogen or (C 1 -C 4)alkyl group and R' 2 is a straight or branched (C 1 -C 6)alkyl group or straight or branched (C 1 -C 6)alkoxy group (ii) a thioethylcarbonyl group of formula wherein R 3 is a straight or branched (C 1 -C 6)alkyl group (iii) a lipophilic chain selected in the group comprising, but not limited to, hexadecyloxypropyl -, octadecyloxyethyl-, oleyloxypropyl-, and oleyloxyethyl-esters), or (b) R' and R" form with the phosphate atom to which they are linked a cycloalkyle group of formula wherein R 4, R 5, R 6, et R 7 each independently represent a straight or branched (C 1 -C 6)alkyl or aryl group or R 4, and R 7 independently represent a straight or branched (C 1 -C 6)alkyl or aryl group or R 5 and R 6 form together an aromatic ring, said aromatic ring being optionally substituted for example by a chloride atom. wherein R 1 represents H, a straight or branched (C 1 -C 6)alkyl group or a -(CH 2) m -R 2 group with R 2 selected from the group comprising hydrogen, halogen, OH, N 3, NH 2, epoxy groups, leaving groups selected from halogen and sulfonyl group and carbonyl groups and m is an integer from 0 to 5, n is an integer from 0 to 5, X and Y independently of each other represent hydrogen, halogen or a straight or branched (C 1 -C 6)alkyl group or an hydroxyethyl group, and R' and R" independently of each other: (a) represent a group selected from the group comprising (i) an oxymethylcarbonyl group of formula wherein R 1 and R' 1 are independently of each other hydrogen or (C 1 -C 4)alkyl group and R' 2 is a straight or branched (C 1 -C 6)alkyl group or straight or branched (C 1 -C 6)alkoxy group (ii) a thioethylcarbonyl group of formula wherein R 3 is a straight or branched (C 1 -C 6)alkyl group (iii) a lipophilic chain selected in the group comprising, but not limited to, hexadecyloxypropyl -, octadecyloxyethyl-, oleyloxypropyl-, and oleyloxyethyl-esters), or (a) represent a group selected from the group comprising (i) an oxymethylcarbonyl group of formula wherein R 1 and R' 1 are independently of each other hydrogen or (C 1 -C 4)alkyl group and R' 2 is a straight or branched (C 1 -C 6)alkyl group or straight or branched (C 1 -C 6)alkoxy group (ii) a thioethylcarbonyl group of formula wherein R 3 is a straight or branched (C 1 -C 6)alkyl group (iii) a lipophilic chain selected in the group comprising, but not limited to, hexadecyloxypropyl -, octadecyloxyethyl-, oleyloxypropyl-, and oleyloxyethyl-esters), or (i) an oxymethylcarbonyl group of formula wherein R 1 and R' 1 are independently of each other hydrogen or (C 1 -C 4)alkyl group and R' 2 is a straight or branched (C 1 -C 6)alkyl group or straight or branched (C 1 -C 6)alkoxy group R 1 and R' 1 are independently of each other hydrogen or (C 1 -C 4)alkyl group and R' 2 is a straight or branched (C 1 -C 6)alkyl group or straight or branched (C 1 -C 6)alkoxy group (ii) a thioethylcarbonyl group of formula wherein R 3 is a straight or branched (C 1 -C 6)alkyl group (iii) a lipophilic chain selected in the group comprising, but not limited to, hexadecyloxypropyl -, octadecyloxyethyl-, oleyloxypropyl-, and oleyloxyethyl-esters), or (b) R' and R" form with the phosphate atom to which they are linked a cycloalkyle group of formula wherein R 4, R 5, R 6, et R 7 each independently represent a straight or branched (C 1 -C 6)alkyl or aryl group or R 4, and R 7 independently represent a straight or branched (C 1 -C 6)alkyl or aryl group or R 5 and R 6 form together an aromatic ring, said aromatic ring being optionally substituted for example by a chloride atom.