The present invention relates to a method for preparing the pyripyropene compound of the formula (I) which method comprises the following steps: i) subjecting a pyripyropene compound of formula Pyripyropene A to an alkaline hydrolysis to yield a 1,7,11 -trideacetylpyripyropene A, ii) reacting 1,7,11-trideacetylpyripyropene A obtained in step i) with cyclopropane carbonyl chloride to yield a raw product containing the pyripyropene compound of formula (I); iii) subjecting the raw product of step ii) to crystallization to yield a crystalline pyripyropene compound of formula (I) and a mother liquor; and iv) recycling the mother liquor or a pyripyropene compound containing fraction thereof to the alkaline hydrolysis of step i).