A variety of imidazo[1,5-a]-1,3,5-triazine derivatives carrying C-, O-, and S-benzyl and/or 4-methylbenzyl groups were synthesized and examined for their inhibitory effects on the replication of ortho- and paramyxoviruses. The key compounds 8-R-2-thioxo-2,3-dihydroimidazo [1,5-a]-1,3,5-triazin-4(1H) …