描述了作为活化氨基酸衍生物的氮杂内酯的第一次催化不对称共轭加成反应向烯酮的发展和进一步发展。第一代方法是从孤立的氮杂内酯开始的,而第二代方法中的氮杂内酯可以从外消旋的N开始原位生成。苯甲酰化氨基酸。第三个进化阶段可以利用外消旋未保护的α-氨基酸直接形成高度对映体富集和非对映体纯的带掩蔽季铵氨基酸产物,并带有一个附加的叔立体中心。通过使用稳固的平面手性bis-Pd催化剂,布朗斯台德酸(HOAc或BzOH; Ac =乙酰基,Bz =苯甲酰基)和布朗斯台德碱(NaOAc),通过协同活化来实现逐步经济转型。特别是第二代和第三代方法提供了快速而多样化的途径,可从廉价的散装化学品中获得生物学上令人感兴趣的非天然季氨基酸衍生物。这样,可以以非对映体纯形式制备高度对映体富集的无环α-氨基酸,α-烷基脯氨酸和α-烷基焦谷氨酸衍生物。此外,
Your wish is my command: Deracemization is a powerful strategy wherein a racemate is converted into a 100 % yield of a single enantiopure product. A new concept in catalyticderacemization is presented, in which a racemate with n stereogenic elements can be selectively converted into each one of 2m (m=number of chiral centers of the product) different enantiopure products, by simple tuning of the reaction
Diastereomers made to order: In an unprecedented ligand‐controlled process a racemic mixture of four stereoisomers can be converted with high selectivity into each one of the diastereomers of the product, at will (see scheme). The mechanism of this deracemization of epimers, that is, a de‐epimerization, was also studied.
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
new atom‐economical method for the synthesis of functionalized cyclobutenes has been developed. This versatile sequence hinges upon a unique combination of an elegant photochemical isomerization and a palladium‐catalyzed alkylation, and converts the readily available, “flat” aromatic 2‐pyrone into a variety of functionalized products with exquisite stereoselectivity.
Diazabutadienes in heterocyclic syntheses. Preparation of pyrimidin-6-ones by reaction of 4-dialkylamino-1,3-diaza-1,3-butadienes with 2-oxazolin-5-ones
作者:Bir Sain、Satyendra P. Singh、Jagir S. Sandhu
DOI:10.1016/s0040-4020(01)81230-8
日期:1992.1
1-aryl-4-dimethylamino-2-methylthio-1,3-diaza-1,3-butadienes ( reacted with 2-oxazolin-5-ones () to yield pyrimidin-6-ones () and () respectively as single diastereoisomers with reverse stereochemistry. Reaction of 1,2-diphenyl-4-methylthio-4-amino-1,3-diaza-1,3-butadienes () with () also yielded pyrimidin-6-ones ().