Approach to the Core Structure of Streptosetin A.

Streptosetin A belongs to the 3‐decalinoyltetramic acids. In contrast to most of other known natural products of this type, the decalin part features a β‐hydroxyketone subunit, making an intramolecular cycloaddition approach less suitable. We examined an approach where the decalin part would be fashioned by an intramolecular aldol addition. By using a Diels‐Alder reaction between the Rawal diene and a substituted methacrylate, a cyclohexanone was obtained. An organocuprate addition introduced the ethyl substituent before, the side chain was converted to an enal. However, contrary to our expectations, the aldol reaction led to the condensation product. Other routes to reach the key cyclohexanone were also investigated. [ABSTRACT FROM AUTHOR]