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

在BF_3.OEt_2的作用下，碳链末端含醛的γ-氧代烯丙基锡以立体控制的方式进行分子内环化反应，得到具有高非对映选择性的七元β-羟基环醚。用该方法合成了一个6-7-7-6环系，作为短链毒素B的模型。在研究过程中，我们发现Bronsted酸催化Bu_4Nf-TiCl4催化的(Z)-Owega-锡醛环化反应生成了正环醚，而(E)-异构体提供了反环醚。为了解释这种立体化学结果，提出了一种推拉机制。用烯丙基锡法尝试了半短杆菌毒素B的全合成，现已完成了6-6-7-7体系的立体控制合成。

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.