Despite
the many methods available for the synthesis of furans,
few methods remain that allow for the custom-made assembly of fully
substituted furans. Here we report a powerful protocol to rapidly
construct tetrasubstituted, orthogonally functionalized furans under
mild reaction conditions. The developed method involves the regioselective
ring-opening of readily available 2,5-dihydrothiophenes followed by
an oxidative cyclization to provide the heterocycle. The selective
oxidation at sulfur is promoted by
N
-chlorosuccinimide
as an inexpensive reagent and proceeds at ambient temperature in high
yield within 30 min. The obtained furans serve as exceptionally versatile
intermediates and were shown to participate in a series of valuable
postmodifications. The fate of the initial sulfonium intermediate
was investigated by mechanistic experiments, and computational studies
revealed the existence of an unprecedented Pummerer-type rearrangement.
The potential for organic synthesis is highlighted by the total synthesis
of bisabolene sesquiterpenoids (pleurotins A, B, and D).
Here we present a comprehensive study
on the [3+2]-cycloaddition
of thiocarbonyl ylides with a wide variety of alkenes and alkynes.
The obtained dihydro- and tetrahydrothiophene products serve as exceptionally
versatile intermediates providing access to thiophenes, dienes, dendralenes,
and vic-quarternary carbon centers. The use of high-pressure
conditions enables thermally unstable, sterically encumbered or moderately
reactive substrates to undergo the cycloaddition under mild conditions,
thereby increasing the yield by up to 58%. In addition, we showcase
its utility by the formal syntheses of the pharmaceuticals NGB 4420
and tenilapine.
We report the design, synthesis and biological evaluation of simplified analogues of the herbicidal natural product (+)‐cornexistin. Guided by an X‐Ray co‐crystal structure of cornexistin bound to transketolase from Zea mays, we attempted to identify the key interactions that are necessary for cornexistin to maintain its herbicidal profile. This resulted in the preparation of three novel analogues investigating the importance of substituents that are located on the nine‐membered ring of cornexistin. One analogue maintained a good level of biological activity and could provide researchers insights in how to further optimize the structure of cornexistin for commercialization in the future.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.