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An efficient and step-economical approach to access functionalized pyrrolizidine derivatives by a one-pot tandem sequence, including an aldol condensation and subsequent 1,3-dipolar cycloaddition process, has been developed, starting from acetone, aldehyde, and proline. A number of substituted aromatic aldehydes were amenable to this transformation, and the desired products, racemic 7a-7w and chiral 9a-9m, were obtained with excellent regioselectivities and outstanding diastereoselectivities. Moreover, in situ NMR studies revealed MgSO4 could effectively promote the aldol condensation pathway in this tandem process. [ABSTRACT FROM AUTHOR]

Microbial constructions of secondary metabolites are generally biosynthetic gene cluster (BGC)-based, and the forging of different BGC-sourced intermediates tends to be overlooked. Here, we show that the dalesconol bioassembly lines in Daldinia eschscholzii can sequester guest intermediates (i.e., building blocks produced outside the dalesconol biosynthetic gene cluster) to form arrays of skeletally undescribed molecules such as (+)-dalescone A, a potent inhibitor against the NLRP3 inflammasome activation. [ABSTRACT FROM AUTHOR]

Autoimmune and inflammatory diseases are associated with inappropriate activation of the NOD-like receptor protein 3 (NLRP3) inflammasome, but suitable inhibitors against such improper activations remain scarce. Here, spirodalesol (1) from Daldinia eschscholzii was structurally characterized and is biosynthetically proposed as an NLRP3 inflammasome activation inhibitor with an unprecedented carbon skeleton. [ABSTRACT FROM AUTHOR]