[Studies of substances with antiviral activity. VI. Activity on Herpes simplex virus of bis-homoanalogs of nucleosides and of hydrazone derivatives of various aromatic substrates].

Derivatives of different chemical structures, namely hydrazones of aromatic compounds and bis-homoanalogues of pyrimidine and purine nucleosides, have been investigated for inhibiting activity on Herpes simplex virus infection of human HEp-2 cell cultures. Some thiosemicarbazones, nucleoside analogues and guanylhydrazones proved active [compounds (I), (II b), (II c), (III), (IV a), (IV b), (V a), (V b); Fig. 1]. An increase in the number of guanylhydrazone chains linked to a fluorene structure [from 1 to 3: compounds (II a), (II b) and (II c)] increased the "activity index" (i.e., toxic versus active concentrations: Table II). Further in vitro investigations have been carried out on bis-guanylhydrazone of 1-phenyl-2-chloro-3,7-diformylindole (I) and it was found that its activity is of the order of 1 microgram per ml (Fig. 3). The compound completely blocks low multiplicity infections while it only blocks cytopathogenicity, not viral replication, in high multiplicity infections.