Total Synthesis of (−)-Chromodorolide B

Abstract

The first total synthesis of a chromodorolide diterpenoid is described. The synthesis features a bimolecular radical addition/cyclization/fragmentation cascade that unites butenolide and trans-hydrindane fragments while fashioning two C–C bonds and stereoselectively forming three of the ten contiguous stereocenters of chromodorolide B

Component‐Tunable Rutile‐Anatase TiO2/Reduced Graphene Oxide Nanocomposites for Enhancement of Electrocatalytic Oxygen Evolution

“…The obtained electrocatalysts exist in the form of rutile-anatase TiO 2 /RGO nanocomposites in which the components of rutile and anatase can be tuned. Benefit from lower activation energy induced by the charge transfer between anatase and rutile, as well as TiO 2 and RGO, the optimized sample exhibits an overpotential as low as 283 mV at 10 mA cm À2 in 1 M KOH, which is superior to the reported TiO 2 (600 mV) [10] and comparable with the leading results of other active materials. [2d,i,j,3d,4a-c,5b-d,6a,10] The fabrication of the rutileanatase/RGO nanocomposites with enhanced OER catalytic activity along with its mechanism investigation may offer a new alternative way for potential electrocatalysts.…”

“…Recently, TiO 2 has been reported to catalyze OER via surface modifications. [10] In detail, the OER activity of TiO 2 can be enhanced by inducing oxygen vacancy defects while it still exhibits a high overpotential of 600 mV at 10 mA cm À2 . [10] So, if we can fabricate an efficient TiO 2 electrocatalyst with a low overpotential, it will be of great significance for the design of electrocatalysts.…”

“…[10] In detail, the OER activity of TiO 2 can be enhanced by inducing oxygen vacancy defects while it still exhibits a high overpotential of 600 mV at 10 mA cm À2 . [10] So, if we can fabricate an efficient TiO 2 electrocatalyst with a low overpotential, it will be of great significance for the design of electrocatalysts. Therefore, in order to explore the application of TiO 2 in the field of electrocatalysis as well as search for more efficient electrocatalysts, it is essential to develop the rare metal-free TiO 2based electrocatalysts with high OER activity.…”

Diastereoselective Coupling of Chiral Acetonide Trisubstituted Radicals with Alkenes

“…Having confirmed that trisubstituted acetonide radicals in this series react with butenolide 4 preferentially in a syn fashion, which is required for the synthesis of (−)-chromodorolide B ( 3 ), [4] we turned to examine structurally more elaborate substrates that harbored the trimethylhydrindane fragment found in 3 (Table 2). Because of the scarcity of the more elaborate radical precursors in this series and limited solubility of diol carboxylic acid precursor 8c , the coupling reactions reported in Tables 1 and 2 were performed under identical conditions at a concentration of 0.1 M in DME.…”

“…It should be recognized that a higher reaction concentration typically improves the yield of bimolecular radical coupling reactions of this type. [4,5] For example, carrying out the coupling reactions of precursors 5c and 8e at 0.4 M instead of 0.1 M increased the yield of the coupled products by more than 30%.…”