Synthetic Studies of Marine Polyketide Ascospiroketal including 5, 5-Spiroketal Moiety

Ascospiroketal A是一种具有特殊三环骨架的海洋聚酮化合物，包括四氢呋喃和5，5-螺酮。以D-(+)-苹果酸为原料，经9步反应合成了磺酮衍生物C7-C11。以L-(+)-酒石酸为原料，经12步反应合成了烷基碘衍生物。以C7-C11链段和C1-C6链段为原料，经脱除1，3-二硫杂环和羟基保护基后，合成了5，5-螺酮缩醛。通过四元不对称碳的构筑和分子内醚化反应，成功地合成了含四氢呋喃环的三环链段。目前正在通过连接三环链段和C12-C16链段来合成子囊菌酮A。

Ascospiroketal A is a marine polyketide having specific tricyclic skeleton including tetrahydrofuran and 5,5-spiroketal.Sufone derivative, segment C7-C11, was synthesized from D-(+)-malic acid by 9 steps. Alkyl iodide derivative, segment C1-C6, was synthesized from L-(+)-tartaric acid by 12 steps. 5,5-Spiroketal segment was synthesized by combination of segment C7-C11 and segment C1-C6 and then the removal of 1,3-dithiane and the protecting group of hydroxy groups. Synthesis of tricyclic segment including tetrahydrofuran ring was successfully carried out by construction of quaternary asymmetric carbon and intramolecular etherification. Total synthesis of ascospiroketal A is currently under way by connection of the tricyclic segment and C12-C16 segment.