A Rapid, Asymmetric Synthesis of the Decahydrofluorene Core of the Hirsutellones

A tandem ketene-trapping/Diels−Alder cyclization sequence was the pivotal transformation in an efficient, asymmetric synthesis of a decahydrofluorene tricyclic structure possessing eight stereogenic centers and key features of the hirsutellone class of antitubercular natural products. The hirsutellone-like β-keto ester that was fashioned by this sequence (13 steps; 6% overall yield) demonstrated significant inhibitory activity against Mycobacterium tuberculosis. The mechanism of action of this antitubercular compound is not yet known.