The syntheses of bis-spiroacetals 28 and 44, model systems for the tricyclic bis-spiroacetal moiety of the polyether antibiotic epi-17-deoxy-(O-8)-salinomycin 3, are described. Introduction of an aldehyde group at C-2 was necessary for further elaboration of the right hand side of the molecule. It was found that the choice of protecting group on the hydroxymethyl substituent (precursor to an aldehyde group) was crucial to the outcome of the key oxidative cyclisation.
