Abstract: Novel guanidino-substituted compounds are described having the following general formula (I): ##STR1## in which X may be carbon, oxygen, nitrogen or sulfur; R.sub.1 may be H, OH, linear or branched lower alkyl, lower alkoxy, lower (alkyl-substituted alkoxy), lower alkyl-amine, lower alkyl-thio, hydroxy substituted lower alkoxy, lower alkoxy-alkoxy substituted lower alkoxy, hydroxy substituted lower alkyl-amine, alkoxy substituted lower alkyl-amine and terminally guanidino-substituted linear of branched lower alkyl, lower alkoxy, lower (alkyl-substituted alkoxy), lower alkyl-amine or lower alkyl-thio; and R.sub.2 and R.sub.3 are independently one of linear or branched lower alkyl, alkoxy, alkyl-substituted alkoxy and alkylamine.These compounds have been found to inhibit effectively herpesvirus replication. Particularly preferred compounds in accordance with formula (I) for this purpose are guanidino-substituted sugar derivatives.