Application of stereocontrolled aldol coupling to synthesis of segments of immunosuppressants FK-506 and rapamycin
作者:James D. White、Jörg Deerberg、Steven G. Toske、Takayuki Yakura
DOI:10.1016/j.tet.2009.06.030
日期:2009.8
The sector comprising C24–C34 of FK-506 containing five of the stereogenic centers in this macrolide was synthesized from (−)-quinic acid. Aldol coupling of the C24–C34 unit with a methyl ketone representing C20–C23 of FK-506 proceeded with complete Felkin stereoselectivity to afford the C20–C34 portion of the immunosuppressant. A chelate transition state invoking coordination of a lithium enolate
由(-)-奎尼酸合成了包含FK-506的C24-C34的区域,该区域在该大环内酯中包含五个立体异构中心。将C24–C34单元与代表FK-506的C20–C23的甲基酮进行Aldol偶联,以完全的Felkin立体选择性进行,得到免疫抑制剂的C20–C34部分。提出了一种使烯醇酸锂与三苯甲基醚配位的螯合过渡态来解释这种立体选择性。FK-506的C26-C34部分构建所采用的策略已扩展到雷帕霉素的C34-C42亚基。使用Mukaiyama不对称抗醛醇偶合剂将大环内酯C26-C33片段中C27,28处的邻二醇功能固定到位。