The cinchona alkaloids are a privileged class of natural products and are endowed with diverse bioactivities. However, for compounds with the closely‐related oxazatricyclo[4.4.0.0]decane (“oxazatwistane”) scaffold, which are accessible from cinchonidine and quinidine by means of ring distortion and modification, biological activity has not been identified. We report the synthesis of an oxazatwistane
diastereoselectivities (>95:5) via a DABCO‐mediated [2+1] annulation. Utilization of enantiomericallypurecinchonaalkaloid derivatives enables the first asymmetric ammonium ylide mediated method to provide (3R , 4R )‐β,γ ‐disubstituted and (2R , 3R, 4R )‐α,β,γ ‐trisubstituted γ ‐butyrolactones in moderate to good yields with up to very good enantiomeric ratios (97:3). The scalability of the transformation
C-5′-Substituted Cinchona Alkaloid Derivatives Catalyse the First Highly Enantioselective Dynamic Kinetic Resolutions of Azlactones by Thiolysis
作者:Carole Palacio、Stephen J. Connon
DOI:10.1002/ejoc.201300451
日期:2013.8
The highly enantioselective dynamickineticresolution (DKR) of azlactones by thiolysis has been achieved for the first time. Although both the parent alkaloid quinine and known C-5′-urea derivatives fail to promote the reaction effectively, a new class of C-5′-hydroxylated catalysts proved capable of catalysing the DKR of a range of azlactones derived from both unbranched- and, previously challenging
首次实现了硫解对吖内酯的高度对映选择性动态动力学拆分 (DKR)。尽管母体生物碱奎宁和已知的 C-5'-尿素衍生物都不能有效地促进反应,但证明了一类新的 C-5'-羟基化催化剂能够催化一系列衍生自无支链和无支链的吖内酯的 DKR。 ,以前具有挑战性的 84-92% ee 的支链氨基酸,包括合成富含对映体的 N 保护硫酯的例子,该硫酯来源于从默奇森陨石中分离的外星氨基酸。