Synthetic studies on dihydroxyheliotridane

Abstract

Synthetic studies on dihydroxyheliotridane were attempted via dihydrofuran intermediate. Cyclization of 4-hydroxyalkene using phenylselenyl chloride, iodine, N-bromosucinimide as electrophiles was performed. Phenylselenoetherification of 4-hydroxyalkene gave trans-2,5-disubstituted tetrahydrofuran as the major product. But trans/cis isomerization occurred in substitution reaction of tosylate 49 to cyanide 51. Cyclization of dihydrofuran 55 using electrophile to bicyclic compound 56 did not succeed. Cis conjugated olefin isomerized in deprotection step unfortunately. Tandem double cyclization of 75 did not succeed. We tried to obtain 89 in various methods in vain. In an attempt to prepare another precursor of tandem double cyclization, we tried to obtain 102. Regioselective deprotection of primary acetate of triacetate 101 resulted in the mixture of 103 and 104 due to the rapid migration of the secondary acetate group to the primary hydroxyl group.