Studies directed toward the total synthesis of antibiotics: (+)-spectinomycin

The presence of a dioxaspiro or a fused bicyclic ring system resulting from a diastereoselective intramolecular acetalization of keto diol or keto alcohol units respectively, is a unique structural feature among a number of biologically important natural products. The particular bond arrangement around the ketal carbon atom is, in part, a reflection of the preference for anomeric stereoselection in nature, either at the site of acetalization or in its vicinity. This phenomenon manifests itself in the constitutional structures of several ionophores (polyether type), in the antibiotic spectinomycin as well as other natural products. Synthetic efforts in this area will be discussed, with particular emphasis on spectinomycin as a challenging target.