The present invention relates to compounds of general formula (I) (I) wherein Cg is -CH2-CIDENTICAL TOCH or -CH2-CH=CH2; R is independently selected from the group consisting of (Cl-C6)alkyl, which may be linear or branched; (C5-C6)cykloalkyl; R1 is H, (C1-C6)alkyl, which may be linear or branched; or (C5-C6)cykloalkyl; R2 to R6 are independently selected from the group consisting of -H, (Cl-C6)alkyl, (Cl- C6)alkoxyl, -N(R7)2, wherein R7 is independently (Cl-C6)alkyl; wherein the compound of general formula (I) bears at least one positive charge. The invention further relates to the methods of synthesis thereof and their use for modification of negatively charged solid surfaces.