NEW MATERIAL:1,5,5-Trimethyl-4-oxabicyclo[4,2,0]octa-3,7-dione.

USE: Synthetic intermediate of lineatin which is an aggregation pheromone of wood borer.

PREPARATION: The objective compound of formula I can be prepared by dissolving 1,5,5-trimethyl-7-hydroxy-4-oxabicyclo[4,2,0]octa-3-dione of formula II in a solvent such as acetone, adding 1W10 equivalent of chromic acid mixture to the solution, and oxidizing the compound of formula II at 0W80°C for 10W60min. The compound of formula II used as the starting compound is obtained from the photo-cyclization addition reaction product of vinyl acetate and a cyclopentenone derivative, according to the reaction formulas.