Synthesis of 2,5‐diisoxazolyltetrahydrofurans

The synthesis of 2,5‐bis(3‐bromo‐5‐isoxazolyl)tetrahydrofuran ( 2 ) and 2,5‐bis(3‐methoxy‐5‐isoxazolyl)tetrahydrofuran ( 3 ) have been accomplished in three and four steps respectively. Cis ‐ and trans ‐isomers have been separated and fully characterized. Differently from synthetic schemes so far utilized for the preparation of the 2,5‐diheteroaryltetrahydrofuran analogs, our approach involves the direct synthesis of a key intermediate containing both isoxazole rings and diol function for the final cyclization. Starting from succinic aldehyde, the new 1,7‐octadiyne‐3,6‐diol ( 4 ) was prepared and was submitted to a double cycloaddition with bromonitrile oxide to yield the key intermediate 1,4‐bis(3‐bromo‐5‐isoxazolyl)‐1,4‐butanediol. The methoxy analogs 3 were obtained by methanolysis of the bromo derivatives 2 .