Asymmetric Total Synthesis of (+)-Attenol B

Abstract

The more cytotoxic, thermodynamically less stable (+)-attenol B was isolated as a minor isomer of the spiroketal attenol A and synthesized previously as a minor product. Herein, we report a new strategy that for the first time led to asymmetric synthesis of (+)-attenol B as an exclusive product, featuring sequential Achmatowicz rearrangement/bicycloketalization to efficiently construct the 6,8-dioxabicyclo[3.2.1]octane core. In addition, (-)-attenol A was obtained with 91% yield by isomerization of (+)-attenol B in CDCl3.