Syntheses of Several Cyclopentano‐Monoterpene Lactones Using 1,3‐ Dioxin Vinylogous Ester.

Formal syntheses of (±)-boschnialactone (5) and three cyclopentano-monoterpene lactones [i.e., (±)-iridomyrmecin (6), (±)-isoiridomyrmecin (7), and (±)-allodolicholactone (8)] have been accomplished in the form of the syntheses of 2-(methoxymethyl)-3-methyl-2-cyclopenten-1-one (11) and (±)-(4aα, 7α, 7aα)-hexahydro-7-methylcyclopenta[c]pyran-3(1H)-one (19), respectively, starting from 6, 7-dihydrocyclopenta-1, 3-dioxin-5(4H)-one (2). A synthesis of (±)-isodehydroiridomyrmecin (9) has also been achieved through a route including direct substitution of the hydroxy group of 2-(tert-butyldimethylsilyloxymethyl)-3-methyl-2-cyclopenten-1-ol (22) with 1-(tert-butyldimethylsilyloxy)-1-methoxyethene (23) as a key step.