A new photoinduced interconversion of four naturally occurring 19-nor-7,8-secolabdane diterpenoids was discovered and analyzed. The photochemical mechanism, intramolecular diradical rearrangement reaction, was investigated by time-lapse monitoring of the end product formations with HPLC and UV, as well as detailed theoretical calculations.
Enantioselective Total Syntheses of Pallambins A–D
syntheses of (-)-pallambins A-D have been achieved in 15 or 16 steps from a known chiral cyclohexenone. Salient features of the syntheses include a palladium-catalyzed oxidative cyclization to assemble the [3.2.1]bicyclic moiety, an Eschenmoser-Claisen rearrangement/lactone formation sequence to construct the C ring, an intramolecular Wittig reaction to form the D ring, and individual transformations of pallambins C