Diastereoselective radical debromination approach toward divergent syntheses of syn- and anti-propionate units, coupled with enantioselective and/or diastereoselective Lewis acid-promoted aldol reactions
作者:Syun-ichi Kiyooka
DOI:10.1016/j.tetasy.2003.06.005
日期:2003.10
methodology directed to the enantioselective synthesis of polypropionate backbones, available for the synthesis of polyketide natural products, has been developed by iterative enantio- and diastereoselective Lewis acid-promoted aldol reactions, followed by diastereoselective radical debromination reactions. A chiral oxazaborolidinone-promoted aldol reaction of a racemic aldehyde, derived from 2-methyl-1
通过迭代对映和非对映选择性路易斯酸促进的醛醇缩合反应,然后进行非对映选择性自由基脱溴反应,已经开发出一种实用的方法学,该方法可用于合成聚酮化合物天然产物,可用于聚丙烯酸酯主链的对映选择性合成。由2-甲基-1,3-丙二醇衍生的外消旋醛与2-溴丙酸乙酯的甲硅烷基乙烯酮缩醛的手性草并氮杂硼硼烷酮促进的醛醇缩合反应导致相应的溴醛羟醛加合物的高度对映选择性形成,然后进行自由基脱溴与卜3 SNH在Et的存在3 B到发散给予顺式-和反-丙醛醇醛缩醛酸酯,是多用途的立体三联体。此外,还实现了丙酸酯单元的延长:手性顺式和反-α-甲基-β-保护的乙醛与甲硅烷基亲核试剂的BF 3 ·OEt 2促进的醛醇缩合反应以基本上完全的顺选择性进行。而TiCl 4促进的羟醛反应导致相当好的抗选择性。通过自由基还原将所得的溴代羟醛加合物发散地脱溴,得到完整的立体四线体。