Quadrane Sesquiterpenes: Natural Sources, Biology, and Syntheses

β-Terrecyclene synthase constructs the quadrane backbone in terrecyclic acid biosynthesis

Quadrane sesquiterpenes featuring a distinctive tricyclic skeleton exhibit potent antimicrobial and anticancer activities. Although extensive studies have attempted to reveal the multistep carbocation rearrangement involved in the formation of the tricyclic quadrane scaffold, the exact biosynthetic pathway and chemical logic to generate the quadrane structure remains mysterious. Here we identified a novel sesquiterpene synthase that is capable of generating β-terrecyclene possessing the quadrane scaffold and characterized the biosynthetic pathway of a representative fungal quadrane terrecyclic acid. Further mutagenesis coupled with isotopically sensitive branching studies of this β-terrecyclene synthase provided insight into the mechanism involved in the formation of the quadrane scaffold.

Disproportionation-Inspired Construction of Highly Functionalized Bicyclo[3.2.1]octanes

The formation of one unavoidable byproduct in traditional disproportionation reactions limits their applications in synthesis. Inspired by convergent disproportionation, we develop an iodine-induced cyclization and oxidation of allylic alcohols to produce highly functionalized bicyclo[3.2.1]octanes through creation of six new bonds. Guided by the mechanism, we elaborated a variety of other bicyclo[3.2.1]octanes bearing distinct groups with presynthesized dienes and enones as the starting materials. This work provides a divergent access to bicyclo[3.2.1]octane frameworks.

Continuous Flow Inter- and Intramolecular Macrolactonization under High Dilution Conditions

An efficient continuous flow process for the macrolactonization of seco acids and diacids using diols in the presence of Mukaiyama reagent (N-methyl-2-chloropyridinium iodide) has been developed for medium to large sized macrocyclic lactones. In comparison with other methods, the continuous flow process provided good to high yield in a short reaction time. By using this methodology, a wide range of macrocyclic lactones (11 compounds), dilactones (15 compounds), and tetralactone derivatives (2 compounds) with various ring sizes (12-26 atoms in the core) were synthesized in just 35 min of residence time. Advantageously, macrolactonization under the flow process is very elegant to handle the high dilution of reactants with a defined perfluoroalkoxy alkanes (PFA) tube reactor volume (7 mL).

Intramolecular Morita-Baylis-Hillman reaction as a strategy for the construction of tricyclic sesquiterpene cores

Starting from a common polyfunctionalized bicyclo[3.2.1]octane-6,8-dione intermediate, a concise synthetic route to tricyclic cores found in quadrane, suberosane, cedrane and related sesquiterpenes was developed using a Morita-Baylis-Hillman intramolecular reaction as a key step.

A switchable dual organocatalytic system and the enantioselective total synthesis of the quadrane sesquiterpene suberosanone

Switch it! The combination of aminocatalysis and N-heterocyclic carbene catalysis has been extended to a switchable dual catalytic system.

First enantioselective total synthesis and configurational assignments of suberosenone and suberosanone as potential antitumor agents

The first enantioselective syntheses of (1R)-suberosenone and (1R)-suberosanone are achieved, leading to revision of the AC of a natural (1S)-suberosanone.