A synthesis of bridged 1,2,4-trioxolanes (bridged ozonides) from 1,5-diketones and hydrogen peroxide catalyzed by SnCl4was developed. It was shown that the ratio of target ozonides can be affected by the application of SnCl4as a catalyst and varying the solvent. A wide range of bridged 1,2,4-trioxolanes (ozonides) was obtained in yields from 50 to 84%. The ozonide cycle was moderately resistant to the reduction of the ester group near the peroxide cycle to alcohol with LiAlH4. The bridged ozonides were evaluated for their antischistosomal activity.These ozonides exhibited a very high activity against newly transformed schistosomula and adultSchistosoma mansoni.