Development of New Synthetic Reactions and their Application to the Synthesis of Biologically Active Compounds

点击翻译按钮获取中文摘要

The BF_3.OEt_2 mediated intramolecular cyclization of the gamma-oxo-substituted allylic tin having an aldehyde group at the terminus of the carbon chain proceeds in a stereocontrolled manner to give the seven membered beta-hydroxy cyclic ether with high diastereoselectivity. This method was applied for the synthesis of a 6-7-7-6 ring system as a model of brevetoxin B. On the way of this investigation we discovered that Bronsted acid catalyzed of Bu_4NF-TiCl_4 mediated cyclization of (Z)-owega-stannyl aldehyde gives syn cyclic ether, whereas (E)-isomer affords anti cyclic ether. To explain this stereochemical outcome, a push-pull mechanism was proposed. By using the allylic tin method, total synthesis of hemibrevetoxin B was attempted, and now have completed the stereocontrolled synthesis of the essential ring framework,6-6-7-7 system.