Diastereoselective Intramolecular Heck Reaction Assisted by an Acetate Group: Synthesis of the Decahydrobenzofluorene Derivative Dasyscyphin E.

The first synthesis of antifungal sesquiterpene quinol dasyscyphin E was achieved starting from trans-communic acid. The process described involves the first diastereoselective synthesis of this type of compound by cyclization of an aryl bicyclosesquiterpene. The acid was efficiently transformed into a sesquiterpene synthon, which was converted into the corresponding bromoaryl sesquiterpene.

First enantiospecific syntheses of marine merosesquiterpenes neopetrosiquinones a and B: evaluation of biological activity.

The first enantiospecific syntheses of neopetrosiquinones A (6) and B (7), two merosesquiterpenes isolated from the deep-water sponge Neopetrosia cf. proxima, from the labdane diterpene trans-communic acid (10) have been achieved. A key step of the synthetic sequence is the simultaneous aromatization of the C ring and the benzylic oxidation on C-7 of an advanced intermediate, mediated by the oxygen-DDQ system.

Synthesis of the putative structure of 15-oxopuupehenoic acid.

Synthesis of the putative structure of the marine natural 15-oxopuupehenoic acid has been achieved starting from commercial (-)-sclareol. Key steps of the synthetic sequence are the Robinson annulation of a β-ketoester and methyl vinyl ketone and an unprecedented cyclization of the resulting α,β-enone, which is mediated by tin(IV) chloride in the presence of N-phenylselenophthalimide. The physical properties of the synthetic compound are somewhat different from those reported for the natural product.

The first synthesis of (-)-isoambreinolide, (+)-vitexifolin D and (+)-vitedoin B.

A very efficient method for synthesizing spirolactones is reported. Treatment of δ,ε-unsaturated carboxylic acids with iodine and triphenylphosphine under mild conditions leads to the corresponding spiro γ-lactones in high yield and with complete stereoselectivity. Utilizing this, the first synthesis of the terpene spirolactones (-)-isoambreinolide, (+)-vitexifolin D and (+)-vitedoin B has been achieved.