Rational synthesis of contra-thermodynamic spiroacetals by reductive cyclizations.
Rational synthesis of contra-thermodynamic spiroacetals by reductive cyclizations.
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DOI：
10.1021/ja044642o
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发表时间：
2005-01
影响因子：
15
通讯作者：
Leo R. Takaoka;A. Buckmelter;Thomas E LaCruz;S. Rychnovsky
中科院分区：
文献类型：
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作者：
Leo R. Takaoka;A. Buckmelter;Thomas E LaCruz;S. Rychnovsky
使用还原环化策略开发了螺缩醛的合成，该策略立体选择性地产生具有单一异头稳定化的螺缩醛。该方法从螺原酸酯的合成开始。原酸酯转化为氰基缩醛。氰基缩醛的还原锂化生成轴向二烷氧基锂试剂，分子内环化生成保留构型的新环。该策略是收敛的，只需几步即可生成复杂的螺缩醛。该方法将可用于天然产物的合成，并将促进以前无法获得的反热力学缩醛的合成。
A synthesis of spiroacetals was developed using a reductive cyclization strategy that leads stereoselectively to spiroacetals with a single anomeric stabilization. The method begins with the synthesis of spiro ortho esters. The ortho ester is converted to a cyano acetal. Reductive lithiation of the cyano acetal generates an axial dialkoxylithium reagent, and intramolecular cyclization produces a new ring with retention of configuration. The strategy is convergent and produces complex spiro acetals in only a few steps. The method will be useful in the synthesis of natural products and will facilitate the synthesis of previously inaccessible contra-thermodynamic acetals.