Macrocylic bisbibenzyl natural products and their chemical synthesis.

Covering: 1995 to June 2011. The macrocyclic bisbibenzyl family of natural products are commonly found in liverworts and other bryophytes, though the recent isolation of riccardin C from a primrose extract has demonstrated their existence in higher flowering plants. Each has a core comprising four aromatic rings and two ethano bridges, being derived in Nature from two molecules of lunularin.

Unified syntheses of cavicularin and riccardin C: addressing the synthesis of an arene adopting a boat configuration.

Concise syntheses of the natural products cavicularin (ten steps) and riccardin C (seven steps) are reported. Key features of the new synthetic route are a convergent strategy to assemble acyclic precursors and a sequence of regioselective reduction and halogenation steps to facilitate Wittig macrocyclisation and transannular ring contraction reactions.

Potassium carbonate-silica: a highly effective stationary phase for the chromatographic removal of organotin impurities.

Organotin impurities in product mixtures can be reduced from stoichiometric levels to approximately 15 parts per million by column chromatography using 10% w/w anhydrous potassium carbonate-silica as a stationary phase.