New synthetic routes to tilorone dihydrochloride and some of its analogues

New synthetic routes to the orally active, interferon-inducing antiviral agent tilorone dihydrochloride, 2,7-bis-[(diethylamino)ethoxy]fluoren-9-one dihydrochloride (1a), were developed. The routes involved the preparation and solvolysis of tetrazonium fluoroborate salts of 2,7-diaminofluoren-9-one. Nonplanar (1b), 9-sulfone (1c), and fluorene (1d) analogues of tilorone dihydrochloride were also prepared. Compounds 1b and 1c were evaluated for interferon induction.