## 3 Chemistry and Biological Activities of Selected Meroterpenoids
The resultant compound could be treated with Barton reaction conditions to undergo decarboxylation, followed by photocatalyzed halogenation reaction to generate the corresponding iodide **226**, which was then converted to diene **227** under basic conditions. Then, electrochemical SET-based [3+2] coupling reaction of diene **227** with phenol **231** via constant potential electrolysis (using reticulated vitreous carbon as cathode and Ni as the anode) generated advanced intermediate **232**. Compound **232** was treated with Mn(dpm)\({}_{3}\) in the presence of TBHP and PhSiH\({}_{3}\) to induce diastereoselective HAT reduction followed by deprotection to generate the natural product stypodiol (**170**) in good yield. Using a similar synthetic protocol, diene **227** was coupled with excess pyrone **214** via single-electron-transfer (SET) to promote a formal [3+2] cycloaddition mediated by cerium ammonium nitrate (CAN) to yield the natural product decaturin (**169**). The iodide intermediate **226** was subjected to nickel-catalyzed cross-coupling with arene iodide **228**, followed by the redox maneuver mediated by CAN and subsequent acid catalyzed intramolecular cyclization provided natural product taondiol (**157a**). Furthermore, iodide intermediate **226** was subjected to nickel-catalyzed cross-coupling with pyrone iodide **229** to afford compound **230**, which upon Lewis acid catalyzed intramolecular cyclization afforded the desired natural product chevalone A (**157**) in good yields [84]. This synthetic strategy offers the opportunity to access many derivatives of these meroterpene natural product derivatives by fine-tuning the coupling partner. The hongoquercins are tetracyclic meroterpenoid natural products with the _trans-transoid_ decalin-dihydrobenzopyran ring system, which display a range of promising bioactivities. This subgroup of the meroterpenoids natural products incorporates a sesquiterpene unit to form the unique hongoquercins. These natural products have attracted attention because they pose a synthetic challenge with four continuous stereocenters and a highly substituted arena scaffold. Access to a modular synthesis can enable the establishment of a medicinal chemistry platform to investigate their exact mode of action. Over the past 25 years multiple synthetic endeavors have been reported towards meroterpenoid (+)-hongoquercin A (**152**, Scheme 18) and (+)-hongoquercin B (**153**, Scheme 19), but a recent simplified approach was disclosed by the [PERSON] group ([PERSON], 2017), featuring a sequential polyketide aromatization and cationic polyene cyclization reaction. The synthesis commenced with thermolysis of dioxane-4\(\beta\)-dione dioxanone **236** in the presence of _trans_, _trans_-farnesyl **234** or geraniol **235** to provide dioxinone \(\beta\)-keto ester **238** or **237** respectively, which upon C-acylation generated the corresponding ester systems. The resultant products underwent highly regioselective decarboxylative allyic rearrangement mediated by Pd\({}_{2}\)dba\({}_{3}\), followed by in situ aromatization to provide farnesyl resorcylate **233** or the geranyl substituted analogue **239** respectively. Compound **233** was then treated with SnCl\({}_{4}\) complex with ligand **240** as a dual Bronsted and Lewis acid, in the presence of SnCl\({}_{4}\) and trifluoracetic acid, which facilitated the enantioselective protonation of the substrate, followed by facile cationic intramolecular polyene cyclization reaction, leading to meroterpenoid **241**. Compound **241** upon saponification provided the natural product (+)-hongoquercin A (**152**). Alternatively, O-allylation of farnesyl resorcylate **233** with allyl bromide under basic condition provided allyl ether **242**, which upon asymmetric dihydroxylation generated diol **244**. This step is followed by mesylating the secondary hydroxyl group, which enables the epoxide formation under a classic Sn\({}_{3}\)2 reaction to provide epoxide **245**.