3 γ-イリデンブテノリド類の新合成法 : (±)-エレモラクトンの合成研究

抄録

Two-step synthesis of γ-ylidenebutenolides has been achieved by dehydration or dealkoxylation of the reaction products of various aldehydes, ketones, and acetals with 2-(trimethylsiloxy)furan in the presence of tin(IV) chloride. This method was applied to the synthesis of 7, 10, and 13. The synthesis of (±)-eremolactone was also examined. In the presence of titanium(IV) chloride, siloxydiene(17) reacted with mesityl oxide to give four diastereoisomeric adducts which structures were presumed as 29a-d. The major isomers(29a, b) gave 30a and 30b respectively by sodium borohydride reduction, though the other two (29c, d) afforded reduced products of acetyl group. Dehydration of 30a followed by functional transformation afforded aldehyde 35a, which was converted to ylidenebutenolide 37a-Z. The double bond migrated comound 38a-Z was revealed to be 9-epimer of (±)-isoeremolactone based on the H^1-NMR spectral data. Therefor the structure of 37a-Z was presumed as shown. The end-exo isomerization of 31a, 35a, and 37a or the transformation of 30b to (±)-eremolactone is under investigation.