aldehydes and stereoselectivity can be flexibly switched in a stepwise manner for the double-aldol reaction. Furthermore, asymmetric triple- and quadruple-aldol reactions are possible in one-pot using the appropriate amounts of donors and amine additives, rapidly elongating the carbon skeleton with controlling up to eight stereocenters. The method should be useful for straightforward synthesis of enantiomerically
我们在这里报告了醛之间的催化不对称迭代和多米诺交叉羟醛反应,具有高度的稳健性、灵活性和通用性。Cu(I)-DTBM-SEGPHOS 复合物催化受体醛和由供体醛衍生的硼烯醇化物之间的不对称交叉羟醛反应,该反应是通过 Ir 催化的烯丙氧基硼酸酯异构化产生的。可以重复使用醛醇产物作为随后不对称醛醇反应的受体底物的单元过程。双醇醛反应的供体醛和立体选择性可以以逐步的方式灵活切换。此外,使用适量的供体和胺添加剂,可以在一锅法中进行不对称的三重和四重醛醇反应,通过控制多达八个立体中心快速拉长碳骨架。该方法可用于直接合成对映异构和非对映异构富集的 1,3-多元醇。
Aldol addition of aldehydes — A stereoselective approach to syn-3-hydroxyaldehydes
TiCl4-aldehyde complexes undergo aldol addition with enolizable aldehydes in the presence of base. The expected 3-hydroxyaldehydes were obtained with a high degree of syn-selectivity.
Titanium Enolates of Thiazolidinethione Chiral Auxiliaries: Versatile Tools for Asymmetric Aldol Additions
作者:Michael T. Crimmins、Kleem Chaudhary
DOI:10.1021/ol9913901
日期:2000.3.1
Asymmetric aldol additions using chlorotitanium enolates of thiazolidinethione propionates proceed with high diastereoselectivity for the "Evans" or "non-Evans" syn product depending on the nature and amount of the base used. With (-)-sparteine as the base, selectivities of 97:3 to >99:1 were obtained for the Evans syn products with 2 equivalents of base and for the non-Evans syn when 1 equiv of base was employed. The thiazolidinethione auxiliaries are easily removed, and the aldol adducts can be readily transformed to various functional groups. Even direct reduction to the aldehyde with diisobutylaluminum hydride is possible.
Total Synthesis of Oxazole-Based Virginiamycin Antibiotics: 14,15-Anhydropristinamycin IIB
作者:David A. Entwistle
DOI:10.1055/s-1998-5935
日期:1998.3
Total Synthesis of Streptogramin Antibiotics. (−)-Madumycin II