Cylindrocyclophane@Ramberg–Backlund

28 August 2010 - Total synthesis

Cylindrophane A Nicolaou 2010  Cylindrocyclophane F's only claim to fame would be being one of the first cyclophanes ever discovered in nature (in an algae) if it wasn't for its tumor-cell cytotoxic properties. The most recent total synthesis effort by the group of K. C. Nicolaou is all about the Ramberg-Bäcklund reaction (DOI). Chunk 1 was dimerised to the di(thioether) by coupling the thioacetate group with the mesylate group with sodium methoxide in methanol followed by oxidation to the bissulfone 2 using hydrogen peroxide and ammonium heptamolybdate. The Ramberg-Bäcklund reaction takes place next with KOH/ Al2O3 the dialkene 3, EE isomerization requiring further treatment with palladium chloride. asymmetric dihydroxylation (AD-mix) gave the tetrol and Barton-McCombie deoxygenation produced the diol 4. In the final steps methylation (mesityl chloride aluminum chloride ) and demethylation (BBr3) produced cylindrocyclophane F.