Copper(I)-Catalyzed Stereodivergent Propargylation of <i>N</i>-Acetyl Mannosamine for Protecting Group Minimal Synthesis of C3-Substituted Sialic Acids
作者:Kouhei Ishizawa、Sohei Majima、Xiao-Feng Wei、Harunobu Mitsunuma、Yohei Shimizu、Motomu Kanai
DOI:10.1021/acs.joc.9b00887
日期:2019.9.6
Copper(I)-catalyzed stereodivergent nucleophilic propargylation at the anomeric carbon of unprotected N-acetyl mannosamine was developed using 3-substituted allenylboronates as a nucleophile. The homopropargylic alcohol products contained two contiguous stereocenters, and two stereoisomers out of the four possible isomers were selectively obtained in a catalyst-controlled manner by applying either
使用3-取代的烯基硼酸酯作为亲核试剂,开发了未保护的N-乙酰甘露糖胺的异头碳上的铜(I)催化的立体发散亲核炔丙基化。均丙醇产物包含两个连续的立体中心,并且通过应用以下任一碱性条件,以催化剂控制的方式选择性地获得了四种可能的异构体中的两种立体异构体:MesCu /(R,R,R)-Ph-SKP催化剂乙(O我PR)3添加剂或酸性条件:a CuBF 4 /(小号,小号,小号)-Ph-SKP催化剂与MEB(O我PR)2添加剂。机理研究表明,取决于条件,会存在不同的活性亲核物质:碱性条件下的烯丙基铜物种或在酸性条件下被路易斯酸性铜催化剂活化的烯丙基硼酸酯。在不使用保护基的情况下,分两步将炔丙基化产物简略地转化为C3-取代的唾液酸。