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手性螺硼酸酯(R)-或(S)-1,1'-联-2-萘酚硼酸-(S)-脯氨酸酐[(R,S)-1或(S,S)-1]对前手性亚胺硼烷还原的不对称催化活性被观察到.在(R,S)-1或(S,S)-1存在下,由前手性二烷基酮或烷基苯酮与苯胺缩合生成的前手性亚胺在THF中被硼烷还原,高产率地给出手性仲胺,其对映体纯度高达74% ee.其中,三种手性仲胺[N-(2-戊基)苯胺,N-(3-甲基-2-丁基)苯胺和N-(4-甲基-2-戊基)苯胺]系首次合成. 相似文献
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以2-溴丙酸和N-叔丁氧羰基-O-苄基-L-丝氨酸为起始试剂首先制得N-(2-溴丙基)-O-苄基-L-丝氨酸(BPBS), 在N,N-二甲基甲酰胺(DMF)/三乙胺(Et3N)溶剂中80 ℃经9 h后BPBS发生分子内环化反应生成(3S,6S)-3-苄氧甲基-6-甲 基-吗啉-2,5-二酮[(3S,6S)-BMMD]及(3S,6R)-BMMD共存体, 产率70%. 将所制得的共存体以乙酸乙酯为重结晶溶剂, 采用微分重结晶法, 经4次“溶解-部分重结晶”操作循环制得两种纯光学构型的(3S,6S)-BMMD和(3S,6R)-BMMD. 将两种光学纯双手性中心的BMMD分别溶于乙酸乙酯, 室温下培养得(3S,6S)-BMMD和(3S,6R)-BMMD的单晶体, 以X射线衍射法测定上述两种BMMD的分子结构. 相似文献
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以高藜芦胺为起始原料,经N-磺酰化反应制得高藜芦磺酰胺(2);2分别与芳乙烯甲醚经对甲苯磺酸催化的Pictet-Spengler反应后用金属钠脱除Ts基团合成了(±)-norlaudanosine(5a)和(±)-O,O-dimethylcoclaurine(5b);使用半量拆分法,以N-乙酰-L-苯丙氨酸为拆分剂,制得(S)-(-)-5a和(S)-(-)-5b,其结构经1H NMR,13C NMR,IR,MS和HR-ESI-MS确证。 相似文献
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A. N. Popkov 《Chemistry of Heterocyclic Compounds》2000,36(5):544-547
The synthesis is reported of (S)-proline derivatives which contain a 2,4,6-trimethyl-, 4-tert-butyl-, or pentamethylbenzyl substituent on the nitrogen atom. Under similar conditions the benzylation of indoline-2-carboxylic acid was unsuccessful. Treatment of indoline-2-carboxylic acid with benzyl chloride in the presence of KOH in dimethylacetamide gave the benzyl ester of N-benzylindoline-2-carboxylic acid which is unstable on light.Laboratory of Biomembranes, University of South Bohemia, Branisovska 31, Ceske Budejovice 37005 Czech Republic. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 625–628, May, 2000. 相似文献
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The Pictet-Spengler cyclization of the imines (3) prepared by the condensation of L-tryptophan methyl ester (1) and aryl methyl ketones (2), using titanium(IV) isopropoxide as an iminating reagent, quantitatively proceeded, when treated with trifluoroacetic acid (TFA) or formic acid, to provide two diastereomers, that is (1S,3S)-1-aryl-3-isopropoxycarbonyl-1-methyl-1,2,3,4-tetrahydro-beta-carbolines (4) and their (1R,3S)-diastereomers (5), of which the diastereomer ratios varied from 1 to 5 depending on the reaction conditions. The (1R,3S)-diastereomers (5) are thermodynamically more stable than their (1S,3S)-congeners (4), as shown by equilibration experiments in TFA. The conversion of 4 to 5 (also 5 to 4) should occur under acidic conditions by cleavage of the C(1)-N(2) bond with complete retention of configuration at the C-3 chiral center. The low diastereo-selectivity observed in the Pictet-Spengler reaction of 1 and 2 is concluded to be a stereochemical outcome under conditions of kinetic control (lower temperature, shorter reaction time), while the high diastereo selectivity with preferential formation of the more stable isomer (5) is the result of thermodynamically controlled experiments (higher temperature, longer reaction time). 相似文献
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13(S)-hydroperoxy- and 13(S)-hydroxyoctadeca-9,11-dienoic acids (1a/b), 15(S)-hydroperoxy- and 15(S)-hydroxyeicosa-5,8,11,13-tetraenoic acids (2a/b), and their methyl esters reacted smoothly with NO2- in phosphate buffer at pH 3-5.5 and at 37 degrees C to afford mixtures of products. 1b methyl ester gave mainly the 9-nitro derivative 3b methyl ester (11% yield) and a peculiar breakdown product identified as the novel 4-nitro-2-oximinoalk-3-enal derivative 4 methyl ester (15% yield). By GC-MS hexanal was also detected among the products. Structures 3b and 4 methyl esters were secured by 15N NMR analysis of the products prepared from 1b methyl ester upon reaction with Na15NO2. 4 methyl ester (14% yield) was also obtained from 1a methyl ester along with the nitrated hydroperoxy derivative 3a methyl ester (10% yield). Under the same conditions, 2a/b methyl esters gave mainly the corresponding nitrated derivatives 5a/b, with no detectable breakdown products, whereas the model compound (E,E)-2,4-hexadienol (6) afforded two main nitrated derivatives identified as 7 and 8. A reaction pathway for 1a/b methyl esters was proposed involving conversion of nitronitrosooxyhydro(pero)xy intermediates which would partition between two competing routes, viz., loss of HNO2, to give 3a/b methyl esters, and a remarkably facile fission leading to 4 methyl ester and hexanal. 相似文献
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Introduction1,4 Diazabicyclo[2 .2 .2 ]octane (DABCO)wasre portedtocatalyzeorganicreactionsduetoitsstrongbasici ty .1,2 Severalchiraltrans 2 ,3 disubstitutedDABCOshavebeensynthesizedandappliedtotheasymmetricBaylis Hillmanreaction3andvicinalhydroxylation .4ThefirstsynthesisofthetitlecompoundwasreportedbySoai5from (2S ,5S) bis(phenylmethyl)piperazine (1) ,asshowninScheme 1.Butthisprocedureislengthy ,andtheoverallyieldisnotsosatisfactory .Besides ,thereport edmethodforthepreparationof 1is… 相似文献
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水饱和离子液体中萘普生的酶法拆分 总被引:1,自引:0,他引:1
考察了五种水饱和离子液体反应介质中固定化脂肪酶催化外消旋萘普生甲酯的水解. 结果表明,这些具有不同阴阳离子组合的咪唑基离子液体作为反应介质都能促进水解反应的有效进行,但在水饱和1-正丁基-3-甲基咪唑六氟磷酸盐([bmim]PF6)中,反应进行得更快,转化率更高. 这些离子液体对脂肪酶均有一定的溶解作用并使溶解的脂肪酶失活. 脂肪酶在离子液体中的溶解度与其剩余活性之间有一定的相关性. 为了解决脂肪酶在离子液体中的溶解问题,使用非极性、高比表面积的无定形多孔硅胶YWG-C6H5对脂肪酶进行了固定化. 在水饱和[bmim]PF6中使用固定化脂肪酶催化反应,反应72 h的转化率为28.3%, 产物的对映体过量值为98.2%, 继续进行反应,转化率将增加,但产物的对映体过量值明显下降. 利用离子液体有别于传统有机溶剂的特性,对离子液体的循环使用、产物的回收和水的补充方法进行了研究. 在反复批式反应中,固定化脂肪酶连续使用五次,活性仅略微下降. 相似文献
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DFT Study on the (S)-Proline-catalyzed Direct Aldol Reaction between Acetone and 4-Nitrobenzaldehyde
1 INTRODUCTION Aldol reaction, one of the most important C–C bond-formation reactions, is widely utilized in orga- nic synthesis[1]. Extensive efforts have been donated to the development of catalytic stereo-selective va- riants of this reaction[2]. However, the direct aldol reaction between unmodified carbonyles would be the most attractive synthetic alternative. Proline-catalyzed intermolecular direct aldol reac- tion between acetone and 4-nitrobenzaldehyde was first reported by List… 相似文献
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Two distinct syntheses of samples of the amino acid L-proline which are stereospecifically deuteriated on the beta-carbon atom are reported. In the first of these, the labelled diazoketones 6, prepared by a chemico-enzymatic synthesis, have been photolysed in alkaline conditions to give the corresponding labelled methyl pyroglutamates 10 via hydrolysis and intramolecular trapping of the resultant ketene intermediates 9. These were then converted into (2S,3S)-[3-(2)H1]- and (2S,3R)-[2,3-(2)H2]-proline, 1a and 1b respectively. The second synthesis provides (2S)-[3,3-(2)H2]-, (2S,3S)- and (2S,3R)-[3-(2)H1]-proline, 1d, 1a and 1c respectively, and has as its key step the highly stereoselective hydrolysis of the silylenol ethers 14 and 14a respectively in which deuteriation or protonation occurs from the re-face of the enol ether. 相似文献