Catalytic and stoichiometric approaches to the desymmetrisation of centrosymmetric piperazines by enantioselective acylation: a total synthesis of Dragmacidin A
作者:Mark Anstiss、Adam Nelson
DOI:10.1039/b608910k
日期:——
The enantioselective desymmetrisation of centrosymmetric piperazines was investigated using both catalytic and stoichiometric asymmetric acylation approaches. The catalytic approach involved the desymmetrisation of 2,5-trans-dimethylpiperazine under the control of chiral DMAP analogues. With one equivalent of piperazine, relative to the acylating agent, low yields of products were obtained in up to
使用催化和化学计量不对称酰化方法研究了中心对称哌嗪的对映选择性脱对称。催化方法涉及在手性DMAP类似物的控制下2,5-反-二甲基哌嗪的不对称化。相对于酰化剂,使用一当量的哌嗪,可在高达70%ee的条件下获得低产率的产品。结果表明,发生了不可避免的“校对”效应,该效应通过其动力学拆分增加了不对称产物的对映体过量。用手性酰化剂[(1R,2R)-N-甲酰基-1,2-双(五氟-苯磺酰胺基)环己烷和(1R,2R)-N-乙酰基-1,2-双(三氟甲烷磺酰胺基)对中心对称哌嗪进行脱对称处理-环己烷]也进行了研究。该方法的产率和对映选择性高度取决于所用溶剂和哌嗪的取代。但是,在某些情况下,对映体过量(最高ee为84%)可以获得良好的对映体富集产物收率(基于手性试剂的最高收率达87%)。该方法被用于德拉莫西丁A的全合成中。