共查询到17条相似文献,搜索用时 156 毫秒
1.
2.
3.
盐酸L-肉碱和盐酸乙酰L-肉碱的合成 总被引:2,自引:0,他引:2
L-肉碱(维生素BT)和乙酰L-肉碱是长链脂肪酸运输的载体, 广泛用于医药、保健食品及饲料等行业. 本工作介绍了一种化学不对称合成盐酸L-肉碱和盐酸乙酰L-肉碱的方法. 以自制的手性噁唑硼烷为催化剂, 将起始原料γ-氯乙酰乙酸乙酯不对称催化氢化还原成(R)-γ-氯-β-羟基丁酸乙酯, 这一步的化学收率和光学收率都较高. 然后将(R)-γ-氯-β-羟基丁酸乙酯转化为盐酸L-肉碱和盐酸乙酰L-肉碱. 合成盐酸L-肉碱只需两步, 总收率为68.3%, ee值可达94.6%; 合成盐酸乙酰L-肉碱需三步, 总收率为62.6%, ee值可达96.8%. 还考察了反应温度、催化剂及还原剂的量等因素对γ-氯乙酰乙酸乙酯的不对称氢化还原的化学产率和光学收率的影响. 相似文献
4.
5.
6.
(S)-和(R)-普萘洛尔的不对称合成 总被引:3,自引:0,他引:3
普萘洛尔是一种临床上广泛使用的β受体阻断剂, 介绍了一种不对称合成(S)-和(R)-普萘洛尔的方法. 以手性Salen-CoIII催化剂水解动力学拆分外消旋环氧氯丙烷得到高光学纯度的(S)-环氧氯丙烷和(R)-3-氯-1,2-丙二醇, 以(S)-环氧氯丙烷为手性原料先水解得(S)-3-氯-1,2-丙二醇, 其与1-萘酚反应得(S)-3-(1-萘基)-丙烷-1,2-二醇, 再与氯化亚砜反应得环状亚硫酸酯, 最后和异丙胺作用得(S)-普萘洛尔, 总收率80.9%, 光学纯度大于99%; 而同样以(S)-环氧氯丙烷为手性原料直接与1-萘酚反应得(2R)-3-(1-萘氧基)-1,2-环氧丙烷, 再与异丙胺作用得(R)-普萘洛尔, 总收率74.5%, 光学纯度大于99%. 相似文献
7.
L-脯氨酸对离子液体介质中的不对称Michael反应催化性能研究 总被引:1,自引:0,他引:1
研究了L-脯氨酸对离子液体介质中醛(酮)与β-硝基烯烃的不对称Michael加成反应的催化性能, 利用X射线单晶衍射对Michael产物结构进行了表征. 结果表明, 反应在遵循胺催化机理的同时, 烯胺是从Re面对β-硝基烯烃进行加成, 产物的优势结构为(1R,2S)的syn型. 脯氨酸在离子液体1-正己基-3-甲基咪唑氯盐中显示良好的催化性能, 室温反应3~5 h, 得到89%以上收率的Michael产物, 其ee值最高70%. 脯氨酸与离子液体形成的催化体系具有良好的重复使用性能, 可至少稳定地重复使用6次. 相似文献
8.
利用易得的光学纯N-甲基氨基醇与1,2-双(二氯磷)乙烷缩合合成了一类新的具有C2对称轴的氮磷-氧磷配体(R,R)-双噁唑啉磷乙烷(BOAPE) 1~4. 该类配体不仅具有C2对称结构和刚性五元环, 还具有富电子特性, 利用500 MHz进行了1H NMR, 31P NMR, 13C NMR表征. 与这些配体配位形成的Rh配合物用于N-苯甲酰基脱氢丙氨酸衍生物和α-功能化酮不对称加氢, 分别可以得到99%和98%的ee. 这类配体比它们相对应的非C2对称的氮磷-氧磷化合物(AMPP)配体具有更高的对映选择性. 在这四个新的配体中配体(R,R)-Ph-BOAPE (2)的催化性能最优. 催化剂[Rh(COD)(R,R)-Ph-BOAPE]BF4的半反应周期t1/2和周转频率(TOF)在N-苯甲酰基肉桂酸甲酯的不对称加氢反应中分别为12 min和6.5 min-1. 相似文献
9.
10.
11.
The 4,5‐methano‐L‐proline was used as chiral organocatalysts in direct asymmetric aldol reactions. Under the optimal conditions, excellent enantioselectivities (up to 99% ee) were obtained with high chemical yields (up to 95%) for a series of aldehydes using only 5 mol% catalyst loading. To show the practicality of the method, the reaction was tested at a large scale. The reaction was complete in 16 h, and the aldol product was obtained in 86% yield and 93% ee. 相似文献
12.
Chunhong Zhang Yuan Qiu Siyuan Bo Fuqingyun Wang Yudan Wang Lijia Liu Yanli Zhou Haijun Niu Hongxing Dong Toshifumi Satoh 《Journal of polymer science. Part A, Polymer chemistry》2019,57(9):1024-1031
A novel one‐handed helical poly(phenylacetylene) bearing L‐hydroxyproline pendants (poly(PA‐P)) was synthesized as an eco‐friendly polymer‐supported catalyst for asymmetric reactions. The helical poly(PA‐P) catalyzed the asymmetric aldol reactions of cyclohexanone with p‐nitrobenzaldehyde, and showed good recyclability and higher enantiomeric excess (ee) in aqueous medias than that in organic medias. The one‐handed helicity of poly(PA‐P) was clearly affected by the water content in the aqueous media. The helical poly(PA‐P) showed the higher enantioselectivity (ee = 99%) than its monomer PA‐P (ee = 54%) in THF/H2O (H2O vol % = 25.0 vol %). After the one‐handed helical structure of poly(PA‐P) was destroyed by grinding treatment, the ee of the reaction clearly decreased from 99 to 49%. These indicate that the one‐handed helical structure of poly(PA‐P) played an important role in the high enantioselectivity of the asymmetric aldol reactions in the aqueous media. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1024–1031 相似文献
13.
Hongwu Zhao Wei Meng Zhao Yang Ting Tian Zhihui Sheng Hailong Li Xiuqing Song Yutong Zhang Sen Yang Bo Li 《中国化学》2014,32(5):417-428
In this work, six novel axially unfixed biaryl‐based water‐compatible bifunctional organocatalysts were designed and synthesized for the organocatalytic access to a variety of 3‐alkyl‐3‐hydroxy‐2‐oxindole derivatives via aldol reactions in water. Organocatalyzed by 5a , the direct aldol reactions of isatins with enolisable ketones underwent readily in water, furnishing the structurally diverse 3‐alkyl‐3‐hydroxy‐2‐oxindoles in various stereoselectivities (up to>99% dr and >99% ee). Moreover, a plausible transition state of the conducted aldol reactions was hypothesized to shed light on the observed stereoselectivities of the obtained 3‐alkyl‐3‐hydroxy‐2‐oxindoles. 相似文献
14.
15.
报道了配合物RuCl2(BISBI)[(R,R)-DPEN] [BISBI=2,2'-二(二苯膦亚甲基)-1,1'-联苯, DPEN=1,2-二苯基乙二胺]的合成和表征, 并研究了其在苯乙酮不对称加氢反应中的催化性能. 考察了底物/催化剂物质的量比、碱浓度、反应温度和氢气压力等对催化活性和对映选择性的影响, 在苯乙酮/KOH/催化剂的物质的量比为30000∶250∶1, 氢气压力为2 MPa, 反应温度为35 ℃时, 苯乙酮的转化率和生成α-苯乙醇的对映选择性分别达到了100%和65% ee. 相似文献
16.
Four L‐proline‐based phosphamides were designed and synthesized as a new kind of organocatalyst. Their catalytic activities for asymmetric direct aldol reactions were evaluated. Among them, 3a with 10 mol% catalyst loading afforded moderate to good yields and up to 99% ee. 相似文献
17.
Isiaka A. Owolabi U.V. Subba Reddy Madhu Chennapuram Chigusa Seki Yuko Okuyama Eunsang Kwon Koji Uwai Michio Tokiwa Mitsuhiro Takeshita Hiroto Nakano 《Tetrahedron》2018,74(36):4705-4711
A new type of amino amide organocatalysts was designed and synthesized from commercially available amino acids in easy steps. Their catalytic activities were examined in enantioselective crossed aldol reaction of various acyclic and cyclic ketones with aromatic aldehydes to afford the corresponding chiral anti-aldol adducts with good to excellent chemical yields, diastereoselectivities and enantioselectivities (up to 99%, up to syn:anti?=?1:99, up to 97% ee). 相似文献