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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.

A dearomative 1,4-carboamination of arenes has been achieved using arenophile cycloaddition and subsequent palladium-catalyzed substitution with non-stabilized lithium enolates. This protocol delivers products with exclusive syn-1,4-selectivity and can be also conducted in an asymmetric fashion. The method allows rapid dearomative difunctionalization of simple aromatic compounds into functional small molecules amenable to further diversification. [ABSTRACT FROM AUTHOR]

Silyl nitronates undergo rhodium-catalyzed formal [3+3]-cycloaddition with enol diazoacetates to form N-silyloxy-3,6-dihydro-2 H-1,2-oxazines. The scope of the reaction and the extent of the major side process were evaluated. A mechanistic scheme was proposed. The nitrogen inversion barrier in the obtained nitroso acetals was estimated based on both quantum calculations and kinetic measurements. [ABSTRACT FROM AUTHOR]