Group-Assisted Purification Chemistry for Asymmetric Mannich-type Reaction of Chiral <i>N</i>-Phosphonyl Imines with Azlactones Leading to Syntheses of α-Quaternary α,β-Diamino Acid Derivatives
作者:Haowei Zhang、Zhen Yang、Brian Nlong Zhao、Guigen Li
DOI:10.1021/acs.joc.7b02556
日期:2018.1.19
An asymmetric Mannich-type reaction between chiral N-phosphonyl imines and azlactones [oxazol-5(4H)-ones] has been established under convenient conditions at room temperature. The reaction was performed without using any bases, additives, or catalysts to achieve up to excellent chemical yields and diastereoselectivity for 32 examples. The α-quaternary syn-α,β-diamino acid products were purified simply
Asymmetric [3 + 2] Cycloaddition of Chiral <i>N</i>-Phosphonyl Imines with Methyl Isocyanoacetate for Accessing 2-Imidazolines with Switchable Stereoselectivity
作者:Shuo Qiao、Cody B. Wilcox、Daniel K. Unruh、Bo Jiang、Guigen Li
DOI:10.1021/acs.joc.6b03068
日期:2017.3.17
Asymmetric [3 + 2] cycloaddition of chiral N-phosphonyl imines with methyl isocyanoacetate has been established, enabling controllable/switchable stereoselectivity access to 21 examples of cycloadducts with good to excellent chemical yields (up to 92%) and high diastereoselectivities (up to 99:1 dr). The cycloadditionreaction promoted by Cs2CO3 resulted in diastereoenriched (4R,5S)-products with >99:1
Group-assisted Purification (GAP) Chemistry/Technology in Synthesizing the Chiral Intermediate of Rivastigmine and Its <i>α</i>-Alkyl Benzylamine Analogues
Introduction of (S)-configuration is the key step in the synthesis of the anti-dementia drug Rivastigmine. Twenty-one alkylation products were obtained through simple washing with hexane/ethyl acet...
Chiral N-phosphonyl imine chemistry: Asymmetric synthesis of α,β-diamino esters by reacting phosphonyl imines with glycine enolates
作者:Teng Ai、Guigen Li
DOI:10.1016/j.bmcl.2009.03.001
日期:2009.7
Chiral phosphonyl imines attached with N-isopropyl protection group were found to react with lithium glycine enolates under convenient conditions to give alpha,beta-diamino esters. Thirteen examples have been examined in good to excellent chemical yields (85-97%) diastereoselectivity (up to 99% de). By treating with HBr at room temperature, the chiral auxiliary can be readily removed and recycled. The absolute structure has been unambiguously determined by converting a product to a known sample. Published by Elsevier Ltd.