脯氨酸二肽催化的不对称直接Aldol反应

以(S)-脯氨酸和(R)-脯氨酸为原料合成了二肽H-(S)-Pro-(S)-Pro-OH(1)和H-(S)-Pro(-R)-Pro-OH(2),分别以两种二肽催化了不对称直接A ldol反应,获得了相同立体构型(S)的产物,与(S)-脯氨酸催化所得的产物构型(R)相反.该催化剂的立体选择性不高(ee<21%).理论计算的结果与实验结果吻合.     

助剂对L-脯氨酸催化直接不对称Aldol反应的影响

在L-脯氨酸催化的芳香醛与丙酮直接不对称aldol反应体系中添加二醇或二酚类助剂可有效提高反应活性.助剂的使用降低了该反应体系中L-脯氨酸的用量.特别是以邻苯二酚为助剂时,最佳反应条件下,仅用5mol％L-脯氨酸与1mol％助剂催化2-硝基苯甲醛与丙酮直接不对称aldol反应,aldol产物产率高达90％,对映选择性为...     

脯氨酸催化剂在不对称反应中的研究进展

脯氨酸作为一种结构简单而且含量丰富的手性分子,近几年来,备受关注,在多种不对称催化反应中表现出非常好的催化性能.综述了这几年来脯氨酸直接催化不对称反应的进展.     

有机催化不对称Mannich反应

有机催化的不对称合成反应是目前研究最为活跃的领域之一.不对称Mannich反应是合成光学活性β-氨基羰基化合物的有效手段.目前报道的催化不对称Mannich反应的有机催化剂主要有脯氨酸及其衍生物、手性磷酸、手性(硫)脲和金鸡纳碱衍生物等,取得了良好的催化活性和对映选择性.本文评述了各类有机催化剂在有机催化不对称Mannich反应中的应用研究进展,以及不对称诱导反应的机理、催化剂分子结构及反应条件对其催化活性和不对称诱导作用的影响.     

壳聚糖负载L-脯氨酸对水中不对称Aldol反应的催化性能

以壳聚糖为载体制备了负载型L-脯氨酸不对称催化剂;将合成产物用于催化丙酮与取代苯甲醛在水中的直接不对称Aldol反应,考察了其催化性能.结果表明,与在有机溶剂中的L-脯氨酸催化剂相比,在水相中的壳聚糖负载L-脯氨酸催化剂表现出更好的催化活性;就间硝基苯甲醛与丙酮在水中的不对称Aldol反应而言,壳聚糖负载L-脯氨酸催化下的产率和ee值分别达95%和48%.此外,壳聚糖负载L-脯氨酸催化剂在水中具有很好的重复使用性能,重复使用10次后相应的产率和ee值分别为88%和68%.     

脯氨酸催化不对称羟醛缩合反应机理研究进展

脯氨酸催化不对称直接羟醛缩合反应是近年来不对称合成研究的热点. 综述并讨论了分子内和分子间不对称直接羟醛缩合的反应机理及其微观过程.     

脯氨酸催化丙酮与异丁醛不对称直接Aldol反应的DFT研究

采用密度泛函DFT-B3LYP方法计算研究了(S)-脯氨酸催化丙酮和异丁醛的不对称直接羟醛缩合(A l-dol)反应,得到了两种烯胺中间体及立体控制步骤中的四个立体异构过渡态的优化构型和相对能量,解释了该不对称反应的立体选择性.     

L-脯氨酸修饰的铱催化苯乙酮及其衍生物不对称加氢反应

在温和条件下制备了L-脯氨酸稳定并修饰的负载型金属铱催化剂,用于苯乙酮及其衍生物不对称催化加氢反应. 考察了L-脯氨酸的量、溶剂、碱以及碱的量和氢气压力对苯乙酮不对称催化加氢反应的影响. 结果显示,该催化剂催化苯乙酮不对称加氢反应获得了92.1%的转化率和32.9%的对映选择性(e.e.),催化2′-(三氟甲基)苯乙醇的对映选择性为39.3,这一结果高于目前报道的天然手性修饰剂修饰的负载型金属催化剂. 该催化循环使用5次, 对映选择性只有小幅度下降.     

有机催化不对称Michael加成反应

有机催化的不对称合成反应是目前研究最为活跃的领域之一. 不对称Michael加成反应是合成众多重要的手性合成子和药物中间体的有效手段. 目前报道的催化Michael加成反应的有机催化剂主要有脯氨酸及其衍生物、手性咪唑啉酮、手性(硫)脲、金鸡纳碱衍生物等. 对各类有机催化剂在有机催化不对称Michael加成反应中的应用, 以及不对称诱导反应的机理、催化剂分子结构及反应条件对其催化活性和不对称诱导作用的影响进行了评述.     

负载脯氨酸及其衍生物催化的不对称C-C键形成反应研究进展

近年来脯氨酸及其衍生物催化的不对称有机反应受到了广泛关注,将其负载于载体上使用也引起了人们的极大兴趣.负载方式大致分为3种:共价键负载,离子对结合或物理吸附等作用负载,以及在离子液体中的两相催化剂.本文对近年来出现的负载脯氨酸及其衍生物催化的不对称反应(Aldol反应、Michael加成反应)研究进展进行了综述.     

High efficient Aldol condensation reaction utilizing modified calcium oxide as stable solid base catalyst

Aldol condensation of acetophenone and benzaldehyde, as well as various benzaldehydes was carried out efficiently to produce chalcone with a good selectivity and high yields by using modified CaO as a solid base catalyst. Stability and catalytic activity of commercial CaO were significantly improved after modifying calcium oxide with bromobenzene in a simple way. An Aldol yield higher than 98.9% was obtained after the reaction was conducted for 3 h. This time interval is considerably shorter when compared to a period of 12 h needed for the commercial CaO to reach 92.1% yield under optimum activation. The high catalytic activity of modified CaO suggests that heterogeneous aldolisation was greatly improved by changing its hydrophilic properties. The influence of several reaction parameters, such as temperature and catalyst loading, was investigated. The humidity test over modified CaO reveals that the basic sites of modified CaO are resistant to CO₂ and moisture. The type of aldehyde has great influence on the yield of Aldol condensation. Based on the results of characterization by Fourier transform-infrared spectrometry (FT-IR) and thermogravimetric measurements (TG), it was concluded that the modifier was chemically bonded to the surface of CaO and nearly no Ca(OH)₂ was formed during the modification process.     

A highly efficient organocatalyst for direct aldol reactions of ketones with aldehydes [corrected

L-proline amides derived from various chiral beta-amino alcohols that bear substituents with various electron natures at their stereogenic centers are prepared and evaluated for catalyzing the direct Aldol reaction of 4-nitrobenzaldehyde with acetone. Catalysts with strong electron-withdrawing groups are found to exhibit higher catalytic activity and enantioselectivity than their analogues with electron-donating groups. The presence of 2 mol % catalyst 4g significantly catalyzes the direct Aldol reactions of a wide range of aldehydes with acetone and butanone, to give the beta-hydroxy ketones with very high enantioselectivities ranging from 96% to >99% ee. High diastereoselectivity of 95/5 was observed for the anti Aldol product from the reaction of cyclohexanone, and excellent enantioselectivity of 93% ee was provided for anti Aldol product from the reaction of cyclopentanone.     

Synthesis of 4,5-disubstituted benzo[c][2,7]naphthyridines as precursors of pyrido[2,3,4-kl]acridones and related natural products

A methodical investigation on functionalization by carbonylated groups in position 4 and 5 of the benzo[c][2,7]naphthyridine skeleton has been undertaken. In particular the study has shown the complex influence of these two sites on each other. A careful choice of both substituents in 4 and 5 permitted the synthesis of an interesting pyrido[2,3,4-kl]acridone tetracyclic structure through an intramolecular Mukayama aldolisation reaction. The structure is supposed to be a potential precursor to various marine alkaloids of the pyridoacridine family.     

Enzymatic Promiscuity： Escherichia coli BioH Esterase-catalysed Aldol Reaction and Knoevenagel Reaction

Esterase BioH,which is obligatory for biotin synthesis in Escherichia coli,was found to exhibit a promiscuous ability to catalyse Aldol and Knoevenagel reactions with moderate to good yields.The reaction conditions including organic solvent,molar ratio of ketone to aldehyde,enzyme amount,and reaction time were investigated to evaluate the effect of different reaction conditions on yield.Target compounds were afforded in the best yield of 91.2％ for Aldol reaction and 54.7％ for Knoevenagel reaction.In addition,because the enzyme could be prepared with a low cost,this protocol could provide an economic route to conduct Aldol and Knoevenagel reactions,which expand the field of enzymatic promiscuity.     

手性磺酰胺有机小分子催化剂在不对称催化反应中的应用进展

有机小分子催化的不对称合成反应是目前研究最为活跃的领域之一.综述了磺酰胺类衍生物作为小分子催化剂在不对称反应(Michael加成反应、Mannich反应、羟醛缩合反应等)中的应用,讨论了磺酰胺中NH的酸性以及氢键性质在不对称催化反应中的的作用.     

Syntheses of (-)-TAN-2483A, (-)-massarilactone B, and the fusidilactone B ring system. Revision of the structures of and syntheses of (+/-)-Waol A (FD-211) and (+/-)-Waol B (FD-212)

The structure of waol A has been revised from 1 to 6, the vinylogue of TAN-2483A (5). Aldol reaction of hydroxybutanolides 13b,c with 2,4-hexadienal affords 12b,c, which are subjected to iodoetherification with bis(sym-collidine)IPF6 to provide 11b(c). Treatment with Et3N in CH2Cl2 completes the three-step syntheses of TAN-2483A (5) and waol A (6). Aldol reaction of hydroxybutanolide 31 with 2,4-hexadienal affords 32, which is subjected to iodoetherification to provide 34, which in turn is treated with Bu3SnCl, NaBH3CN, and oxygen to provide diol 60. Further elaboration completes the first syntheses of massarilactone B (7) and the fusidilactone B (9) ring system.     

(S)-N-取代-1,2,3,4-四氢异喹啉-3-甲酰胺催化直接不对称Aldol反应研究

本文研究了以(S) -N-取代-1,2,3,4-四氢异喹啉-3-甲酰胺衍生物的有机小分子催化剂催化不对称Aldol反应,得到高达92%收率和57%的ee值.     

Helical Polymer as Mimetic Enzyme Catalyzing Asymmetric Aldol Reaction

This Communication reports optically active helical substituted polyacetylenes which solely catalyzed asymmetric Aldol reaction between cyclohexanone and p‐nitrobenzaldehyde; more importantly the helical structures are found to play crucial roles in the asymmetric catalysis, with a remarkable yield and ee (both up to 80%). A synergic effect is observed between the helical structures in the polymer main chains and the pendent prolinamide moieties for successfully catalyzing the asymmetric reaction. The role of the helical polymer backbones is further verified by tuning the relative helical structure content.     

The role of pyruvic acid as starting material in some organic reactions in the presence of SBA-Pr-SO<Subscript>3</Subscript>H nanocatalyst

Pyruvic acid contains three different reactive positions: –COOH, ketone carbonyl and methyl groups. Correspondingly, pyruvic acid was applied as starting material in the modified Niementowski reaction and Aldol condensation using SBA-Pr-SO₃H as an efficient nanocatalyst. Aldol condensation of pyruvic acid and oxindole provided a new oxindol-based carboxylic acid which was subsequently used in the Ugi four-component reaction. Moreover, through the modified Niementowski reaction of pyruvic acid, new derivatives of quiazoline were produced in the presence of SBA-Pr-SO₃H. The obtained products are important due to their potentially biological active skeletons.     

模拟醛缩酶催化不对称直接Aldol反应新进展

对天然醛缩酶的作用机理进行了一般性阐述，在此基础上详细回顾了近几年对 两类醛缩酶的模拟催化不对称直接Aldol反应，并对其发展前景作了展望。