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The sesquiterpene-tropolones belong to a distinctive structural class of meroterpene natural products with impressive biological activities, including anticancer, antifungal, antimalarial, and antibacterial. In this article, we describe a concise, modular, and cycloaddition-based approach to a series of sesquiterpene mono- and bistropolones, including (-)-epolone B, (+)-isoepolone B, (±)-dehydroxypycnidione, and (-)-10- epi -pycnidione. Alongside the development of a general strategy to access this unique family of metabolites were computational modeling studies that justified the diastereoselectivity observed during key cycloadditions. Ultimately, these studies prompted stereochemical reassignments of the pycnidione subclass and shed additional light on the biosynthesis of these remarkable natural products.

Modern drug discovery efforts rely, to a large extent, on lead compounds from two classes of small organic molecules; namely, natural products (i.e., secondary metabolites) and designed compounds (i.e., synthetic molecules). In this article, we demonstrate how these two domains of lead compounds can be merged through total synthesis and molecular design of analogs patterned after the targeted natural products, whose promising biological properties provide the motivation. Specifically, the present study targeted the naturally occurring biyouyanagins A and B and their analogs through modular chemical synthesis and led to the discovery of small organic molecules possessing anti-HIV and anti-arenavirus properties.

Isolated from Hypericum species H. chinese L. var. salicifolium, biyouyanagin A was assigned structure 1a or 1b on the basis of NMR spectroscopic analysis. This novel natural product exhibited significant anti-HIV properties and inhibition of lipopolysaccharide-induced cytokine production. Described herein are the total syntheses of biyouyanagin A and several analogues (3-11), structural revision of biyouyanagin A to 2b, and the biological properties of all synthesized compounds. The total synthesis proceeded through cascade sequences that efficiently produced enantiomerically pure key building blocks 15b (ent-zingiberene) and 18 (hyperolactone C) and featured a novel [2 + 2] photoinduced cycloaddition reaction which occurred with complete regio- and stereoselectivity. Biological investigations with the synthesized biyouyangagins A (2-11) and hyperolactones C (12-16) revealed that the activity of biyouyanagin A most likely resides in its hyperolactone C structural domain.