A New Synthesis of 1,5-Di-tert-butyl-1,3-cyclopentadiene by Dehydration of an Epoxide and Characterization of its Diels−Alder Dimer

Divergent and gram-scale syntheses of (-)-veratramine and (-)-cyclopamine

Veratramine and cyclopamine, two of the most representative members of the isosteroidal alkaloids, are valuable molecules in agricultural and medicinal chemistry. While plant extraction of these compounds suffers from uncertain supply, efficient chemical synthesis approaches are in high demand. Here, we present concise, divergent, and scalable syntheses of veratramine and cyclopamine with 11% and 6.2% overall yield, respectively, from inexpensive dehydro-epi-androsterone. Our synthesis readily provides gram quantities of both target natural products by utilizing a biomimetic rearrangement to form the C-nor-D-homo steroid core and a stereoselective reductive coupling/(bis-)cyclization sequence to establish the (E)/F-ring moiety.

2,5-Diphenyl-3,4-bis(2-pyridyl)cyclopenta-2,4-dien-1-one as a Redox-Active Chelating Ligand

2,5-Diphenyl-3,4-bis(2-pyridyl)cyclopenta-2,4-dien-1-one (1), a close relative of tetraphenylcyclopentadienone, is a new ligand platform for use in redox switches and sensors. Compound 1 acts as a molecular electrochemical sensor towards a range of divalent metal ions and exhibits favourable two-wave behaviour. It forms chelates of the type [(1)MX2], whose stability is enhanced by five orders of magnitude upon one-electron reduction. The bite angle of 1 is close to 90 degrees in these complexes. The attachment of the 14-valence-electron Cp*Co fragment to the cyclopentadienone pi system reduces the bite angle and thus modulates the binding characteristics of 1.