Synthesis of novel tetraacetal oxa-cage compounds from 2-methylthiofurans

Abstract

Several novel tetraacetal oxa-cage compounds 9a-9f were synthesized from the corresponding 2-methylthiofurans 1a-1f by a short sequence. The structures of these tetraoxa-cage compounds were deduced from their spectral data and proven by X-ray analysis of 9a. Ozonolysis of the endo adducts 5a-5f in CH2Cl2 at -78 degrees C followed by reduction with dimethyl sulfide gave the tetraoxa-cages 9a-9f in 65-75% yields, respectively. Ozonolysis of the exo adduct 6a under the same reaction conditions gave the tetracarbonyl compound 10. The phenylthio group substituted tetraoxa-cage 13 and the tetraacetal oxa-cage 17, with one more carbon atom on the apex position, were also synthesized in a similar sequence.