Enantioselective synthesis of A 3,5,5-trialkylated tetronic acid derivative

A convenient and enantioselective method for the synthesis of 3,5,5-trialkylated tetronic acid has been developed. The Dieckmann-type condensation of enantioenriched a-acyloxy-a,a-dialkylated acetic acid ester (11) proceeded in the presence of lithium hexamethyldisilazide, providing the expected tetronic acid derivative (12) after quenching with methoxymethyl chloride. The product (12) was converted into a doubly prenylated tetronic acid derivative (13), which constitutes a substructure of perforatumone, a newly isolated polycyclic polyprenylated acylphloroglucinol-type natural product.