Hanfeng Ding

Total Synthesis of Echinopines A and B

Echinopines A and B [(+)-1 and (+)-2], two naturally occurring compounds characterized with a unique [3.5.5.7] carbon framework, have been synthesized in both enantiomeric and racemic forms. Their total synthesis involves a novel intramolecular rhodium-catalyzed cyclopropanation (4 --> 16) and a samarium diiodide-mediated ring closure (3 --> 37).

Highly Efficient Access to Iminoisocoumarins and α-Iminopyrones via AgOTf-Catalyzed Intramolecular Enyne−Amide Cyclization

Iminoisocoumarins and alpha-iminopyrones are prepared via Sonogashira coupling and AgOTf-catalyzed 6-endo-dig O-cyclization of the enyne-amide system in dichloroethane, in one pot or stepwise, respectively.

Synthesis of 2-Vinylbenzofurans via the Copper-Catalyzed Multicomponent Reactions Involving an Oxa-Michael/Arylation/Vinylation Cascade

2-Vinylbenzofurans have been synthesized via the copper-catalyzed one-pot, three-component reactions of o-iodophenols, in situ generated allenes, and dichloromethane. Cascade transformation of oxa-Michael addition, C-arylation, and sp(3)C-H/sp(3)C-Cl conversion-based vinylation has been involved in realizing the construction of this 2-vinylbenzofuran framework.

Divergent Total Synthesis of Indoxamycins A, C, and F**

As a novel class of polyketides, indoxamycins A–F were isolated in 2009 by Sato et al. from saline cultures of marinederived actinomycetes. Within this family, indoxamycins A and F have exhibited promising growth-inhibition activity against HT-29 tumor cell lines (IC50= 0.59 mm and 0.31 mm, respectively), thus achieving levels of activity similar to that of mitomycin (IC50= 0.66 mm). The absolute and relative stereochemistry of indoxamycins was originally assigned based on a combination of oneand two-dimensional NMR experiments and CD studies (Scheme 1a). The indoxamy-

Total Synthesis of Diterpenoid Steenkrotin A

A concise and diastereoselective total synthesis of the diterpenoid (±)-steenkrotin A is described for the first time. The strategy mainly features three key ring formations: 1) a rhodium-catalyzed O-H bond insertion followed by an intramolecular carbonyl-ene reaction to build up the tetrahydrofuran subunit; 2) sequential SmI2 -mediated Ueno-Stork and ketyl-olefin cyclizations to construct the [5,7] spirobicyclic skeleton; and 3) an intramolecular aldol condensation/vinylogous retro-aldol/aldol sequence to form the final six-membered ring with inversion of the relative configuration at the C7 position.

Total Syntheses of Highly Oxidized ent-Kaurenoids Pharicin A, Pharicinin B, 7-O-Acetylpseurata C, and Pseurata C: A [5+2] Cascade Approach

The unprecedented oxidative dearomatization-induced [5+2] cycloaddition/pinacol-type 1,2-acyl migration cascade efficiently generates a quaternary carbon center and assembles the highly oxygenated bicyclo[3.2.1]octane framework of ent-kaurene diterpenoids. By incorporation of the subsequent retro-aldol/aldol process and singlet oxygen ene reaction, this concise and convergent approach has enabled the first asymmetric total syntheses of pharicin A, pharicinin B, 7-O-acetylpseurata C, and pseurata C.

Total Synthesis of Indole Alkaloid Alsmaphorazine D

A concise total synthesis of rac-alsmaphorazine D has been described for the first time. The efficient synthetic strategy features four key transformations: 1) a catalytic intramolecular oxidative cyclization for the δ-lactamindole backbone; 2) an oxidative cyclic aminal formation for the hexahydropyrrolo[2,3-b]pyrrole framework; 3) a transannular radical cyclization for the construction of the diazabicyclo[3.3.1]nonane structure; and 4) a one-pot desilylation/double epimerization reaction that affirms the relative stereochemistry.

Diastereoselective total synthesis of salvileucalin C.

A concise and efficient approach for the diastereoselective total synthesis of salvileucalin C, as well as their biosynthetically related diterpenoids salvileucalin D, salvipuberulin, isosalvipuberulin, and dugesin B, has been reported for the first time. The key features of the strategy are based on a Beckwith-Dowd ring expansion, a tandem diastereoselective Stille coupling/debromination/desilylation/lactonization reaction, and a photoinduced electrocyclic ring contraction.

Stereoselective Total Synthesis and Structural Elucidation of (-)-Indoxamycins A-F

In this study, a concise and stereoselective approach for the divergent total synthesis of (-)-indoxamycins A-F is described. The key steps of the strategy include an Ireland-Claisen rearrangement, an enantioselective 1,6-enyne reductive cyclization, and a tandem 1,2-addition/oxa-Michael/methylenation reaction. The relative and absolute configuration of these natural products has been unambiguously elucidated, and their cytotoxic activities against HT-29 and A-549 tumor cell lines are also reported.

Diastereoselective Total Synthesis of the Euphorbia Diterpenoid Pepluanol A: A Reductive Annulation Approach

A new titanium(III)-catalyzed reductive annulation constructed a series of diversely functionalized 1,5-diols in good to excellent yields with respect to a wide scope of vinyl epoxide-aldehyde substrates. Taken together with a Diels-Alder reaction and a substrate-controlled diastereoselective cyclopropanation as additional key steps, the synthetic utility of this novel method has been preliminarily explored by the first and concise total synthesis of the Euphorbia diterpenoid (±)-pepluanol A.