To systematically investigate the influence of the variation of the original skeletons and spatial configuration of 2,3-fused indole natural products on antiviral activities, two types of structurally novel and potent pseudo-indole natural product derivatives, 1,2-fused indole and spiroindoline, with different substituents were direct synthesized from 2-halo anilines, and their antiviral activities against tobacco mosaic virus (TMV) were evaluated. The results showed that these compounds exhibited good anti-TMV activity, especially 3f, 3g, 3i, 5e, 5h, and 5l, which were more potent than the commercial anti-virus agent ribavirin. An SAR investigation demonstrates that the original ring size, arrangement, and planarity are not optimal; their anti-TMV activities can be improved by skeleton modification and spatial configuration variation. Both of the structurally novel skeletons provide a new template for antiviral studies, which may also provide some useful information for antiviral mechanism elucidation.
Keywords: 1, 2-Fused indole; Anti-TMV; Pseudo-indole alkaloids; Spiroindoline; Tobacco mosaic virus.