Synthesis and synthetic studies towards diterpenes, sesquiterpenoids, and the caged Garcinia xanthones

The synthesis and the biological evaluation of a new family diterpenes are presented. The synthetic studies were inspired by the structural framework of acanthoic acid and yielded a family of compounds that were evaluated as anti-inflammatory agents. Our findings suggest that these diterpenes represent promising leads for the development of novel anti-inflammatory agents. A short, efficient approach to construct germacrolide core is described. During the research, the tandem Payne-Grob reaction and double Payne-Grob reaction cascade were developed. The reactions were useful to construct ten- membered cyclic precursors. The new approach provides an enantiomeric method to synthesize natural products such as germacrolides, pseudoguainolides, and briaranes. The development is unique from all others by its bond installations and functional-group transformations. The synthetic studies towards the caged Garcinia xanthones are reported. The model caged Garcinia xanthones and forbesione were constructed through a biomimetic tandem Claisen/Diels-Alder rearrangement. The effects of temperature and solvents on this reaction cascade were examined. Different Lewis acids were tested as catalysts for the tandem Claisen/Diels-Alder rearrangement. Among them, lanthanide (III) complexes were the best to accelerate the reaction since they exhibit their catalytic effect in both polar and non-polar solvent