SYNTHESIS OF (+ -)-PYRENOLIDE-B

In the synthesis of the title compound 12, the important intermediate 7 was obtained in good yield from the easily available ethyl 5,5-ethyl enedioxy-2-oxocyclohexane-1-carboxylate (1) via ring enlargement of th e bicyclic enol ether 5 (Scheme). Its reduction (NaSH4, CeCl3 in EtOH) and subsequent protection with (t-Bu)Me(2)Si resulted in the highly f unctionalized ten-membered lactone 9. Introduction of the (Z)-configur ated double bond, followed by deprotection and elimination of H2O, gav e (+/-)-pyrenolide B (12) in 16 % overall yield.