Discovery and bioinspired total syntheses of unprecedented sesquiterpenoid dimers unveiled bifurcating [4+2] cycloaddition and target differentiation of enantiomers

[4 + 2] cycloaddition has led to diverse polycyclic chiral architectures, serving as novel sources for organic synthesis and biological exploration. Here, an unprecedented class of cadinane sesquiterpene [4 + 2] dimers, henryinins A-E (1-5), with a unique 6/6/6/6/6-fused pentacyclic system, were isolated from Schisandra henryi. The divergent total syntheses of compounds 1-5 and their enantiomers (6-10) were concisely accomplished in eight linear steps using a protection-free approach. Mechanistic studies illustrated the origin of selectivity in the key [4 + 2] cycloaddition as well as the inhibition of reaction pathway bifurcation via desymmetrization. The chemical proteomics results showed that a pair of enantiomers shared common targets (PRDX5 C100 and BLMH C73) and had unique targets (USP45 C588 for 4 and COG7 C419 for 9). This work provides experimental evidence for the discovery of unprecedented cadinane dimers from selective Diels-Alder reaction and a powerful strategy to explore the biological properties of natural products. The [4 + 2] cycloaddition has led to diverse polycyclic chiral architectures, serving as novel sources for organic synthesis and biological exploration.

Automated summary

This study reported an unprecedented class of cadinane sesquiterpene [4+2] dimers, which were synthesized using a protection-free approach, and revealed the origin of selectivity in the key [4+2] cycloaddition and the mechanism of inhibition of reaction pathway bifurcation. Chemical proteomics results showed that these compounds had multiple targets. This work provides experimental evidence and a powerful strategy for the discovery of novel compounds and exploration of the biological properties of natural products.