Bioinspired concise synthesis of caged Sesquiterpenoids Artatrovirenols A and B.

Artatrovirenols A and B are two newly isolated sesquiterpenoids with a complex caged framework. We report herein a concise synthesis of artatrovirenols A and B in 9 and 8 steps, respectively. The complex caged tetracycle is rapidly constructed from a known planar guaiane-type precursor through a bioinspired intramolecular [4 + 2] cyclization to firstly access artatrovirenol B, which is further transformed into artatrovirenol A through a biomimetic epoxidation-mediated lactonization reaction.

Total Syntheses of Phleghenrines A and C: A [4 + 2] Cycloaddition and Ring-Expansion Approach.

The first total syntheses of alkaloids phleghenrines A and C have been accomplished in 19 and 18 steps, respectively, relying on three (hetero)-Diels-Alder ([4 + 2]) cycloaddition reactions to forge the cyclic molecular backbone and two ring-expansion reactions to manipulate the ring size. A chiral precursor is synthesized through an auxiliary controlled Diels-Alder reaction, rendering the asymmetric synthesis accessible. The established strategy provides a general approach to the relevant novel alkaloids.