共查询到20条相似文献,搜索用时 15 毫秒
1.
Fred van Rantwijk Michiel A. P. J. Hacking Roger A. Sheldon 《Monatshefte für Chemie / Chemical Monthly》2000,72(8):549-569
The lipase-catalyzed aminolysis of carboxylic esters is a fairly general reaction that has been performed with a wide range of esters and amines, generally in anhydrous organic media to avoid undesirable hydrolysis of the ester. Alternatively, carboxylic amides can be synthesized by lipase mediated condensation of carboxylic acids and amines if an excess of either reactant is avoided. Chiral carboxylic esters have been resolved by lipase-catalyzed aminolysis. In the majority of these resolutions, Candida antarctica lipase B has been employed as the catalyst. A range of chiral amines has been resolved by lipase mediated acylation, using mainly the lipases from C. antarctica (B type) and Pseudomonas species. The enantiorecognition was frequently found to depend critically on the acylating agent and the reaction medium. 相似文献
2.
Erik Henke Sascha Schuster Hong Yang Uwe T. Bornscheuer 《Monatshefte für Chemie / Chemical Monthly》2000,131(6):633-638
Summary. The resolution of ibuprofen by transesterification of its corresponding vinylester using lipase B from Candida antarctica is described. Compared to transesterification or hydrolysis of the ibuprofen ethyl ester (E < 2, 28–48 h), the reaction with vinylesters occurred significantly faster (1.5–5 h) and with considerably higher enantioselectivity
(E = 8–39).
Received December 20, 1999. Accepted January 12, 2000 相似文献
3.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1459-1466
Abstract We have developed novel polymeric systems that aggregate in aqueous media to form nanospheric particles. Our polymeric system constitutes guanidine functional groups and poly(ethylene glycol) (PEG) units. The guanidine group is an important structural component in many biologically active compounds. Because of their strongly basic character, guanidines are fully protonated under physiological conditions. The positive charge thus imposed on the molecule forms the basis for specific interactions between the ligand and receptor or the enzyme and substrate. The PEG units may form a characteristic micelle structure with a hydrophilic shell layer surrounding the core of the polyion complex (PIC) formed between DNA and the cation segments (PIC micelles). 相似文献
4.
Summary. Dimers of substituted acetylenic amides were obtained when triethylamine was used as refluxing solvent and acid acceptor
instead of pyridine in the reaction of substituted acetylenic amides with triphosgene. Unsubstituted acetylenic amides resulted
in the corresponding quinazolinone.
Received October 22, 2001. Accepted (revised) November 22, 2001 相似文献
5.
Enzo Santaniello Patrizia Ferraboschi Shahrzad Reza-Elahi 《Monatshefte für Chemie / Chemical Monthly》2000,131(6):617-622
Summary. Lipase from Pseudomonas cepacia (PCL) catalyzes the regio- and stereoselective acylation of primary and secondary hydroxy groups in steroid side chains under
irreversible transesterification conditions with vinyl acetate in organic solvents.
Received December 20, 1999. Accepted December 31, 1999 相似文献
6.
Moslem M. Lakouraj Barahman Movassagh Zahra Fadaei 《Monatshefte für Chemie / Chemical Monthly》2002,133(8):1085-1088
Summary. Various thiol esters were prepared by condensation of acyl chlorides with disulfides in the presence of Zn/AlCl3. The advantages of this method are high yields under relatively mild conditions, simple work-up, lack of toxicity, and low
costs.
Received July, 20, 2001. Accepted September 24, 2001 相似文献
7.
Christian Amatore Anny Jutand Jacques Périchon Yolande Rollin 《Monatshefte für Chemie / Chemical Monthly》2000,131(12):1293-1304
Summary. The mechanism of the nickel-catalyzed electrosynthesis of ketones by heterocoupling of phenacyl chloride and benzyl bromide
has been investigated by fast scan rate cyclic voltammetry with [Ni(bpy)2+
3](BF4
−)2 as the catalytic precursor (bpy = 2,2{−}{ bipyridine}). The key step is an oxidative addition of Ni0(bpy) (electrogenerated by reduction of the Ni(II) precursor) to PhCH2Br whose rate constant is found to be 10 times higher than that of PhCH2COCl. The complex PhCH2NiIIBr(bpy) formed in the oxidative addition is reduced at the potential of the NiII/Ni0 reduction by a two-electron process which affords an anionic complex PhCH2Ni0(bpy)− able to react with PhCH2COCl to generate eventually the homocoupling product PhCH2COCH2Ph. The formation of the homocoupling product PhCH2COCOCH2Ph is prevented because of the too slow oxidative addition of Ni0(bpy) to PhCH2COCl compared to PhCH2Br. The formation of the homocoupling product PhCH2CH2Ph is also prevented because PhCH2Ni0(bpy)− does not react with PhCH2Br. This explains why the electrosynthesis of the ketone can be performed selectively in a one-pot procedure, starting from
an equal mixture of PhCH2COCl and PhCH2Br and a nickel catalyst ligated by the bpy ligand.
Received June 27, 2000. Accepted July 11, 2000 相似文献
8.
Summary. Amphiphilic porphyrins with a bola-type arrangement of trimethylammonium headgroups can be used to generate M41S-type silica
mesostructures with a lamellar topology and alternating organic–inorganic layers. Within the organic layers, the porphyrin
entities are aggregated as shown by UV-Vis spectroscopy. The use of a bola amphiphile as structure-directing agent extends
the possibilities of surfactant-controlled assembly of inorganic structures. In addition, the direct functionalization of
the organic part of organic–inorganic hybrid nanostructures is possible due to the combination of the amphiphilic function
with that of a chromophore.
Corresponding author. E-mail: peter.behrens@mbox.acb.uni-hannover.de
Received February 22, 2002; accepted May 8, 2002 相似文献
9.
Summary. Various heteroaromatic N-oxides were efficiently deoxygenated to the corresponding bases under mild conditions using formamidinesulfinic
acid (thiourea S,S-dioxide).
Received March 24, 2000. Accepted April 18, 2000 相似文献
10.
Justin O. Brower David A. Lightner 《Monatshefte für Chemie / Chemical Monthly》2001,132(12):1527-1546
Summary. Analogs of bilirubin with vinyl groups replaced by symmetrically-disposed o-fluorophenyls (1, bis-exo, and 2, bis-endo) were synthesized and characterized spectroscopically. Their 1H NMR spectra and NOE data are consistent with an intramolecularly hydrogen-bonded ridge-tile conformation where each propionic
acid group embraces an opposing dipyrrinone. Like bilirubin, 1 and 2 exhibit negative chirality induced circular dichroism (ICD) Cotton effects in chloroform containing quinine. Unlike bilirubin, however, in aqueous buffer containing human serum albumin, 2 exhibits a negative exciton chirality ICD, whereas that of 1 is positive.
Received May 22, 2001. Accepted May 29, 2001 相似文献
11.
Mukesh K. Pandey Rahul Tyagi Bhavna Gupta Virinder S. Parmar Jayant Kumar Arthur C. Watterson 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):931-937
Polymer nano-particles have been widely investigated in the last decade due to a variety of potential applications. In particular, polymers which can self assemble into micellar nano-particles can be effectively used as vehicles for drug delivery. Considerable efforts are underway to develop better drug delivery nano carriers for high drug loading capacity for a wide variety of bioactive compounds. In this study, several new polymers were synthesized in bulk (solventless condition) by a chemo-enzymatic methodology using Candida antarctica lipase B (Novozyme 435) and molecular sieves (MS). The synthesized polymers demonstrated high drug loading capacity and the potential to encapsulate drugs which are poorly soluble in aqueous solvents. 相似文献
12.
Magdolna Solymár Márta Palkó Tamás Martinek Ferenc Fülöp 《Monatshefte für Chemie / Chemical Monthly》2002,133(11):1423-1430
Summary. The reactions of 1,2,3,4-tetrahydro-β-carboline-1-carboxylic acid and its ethyl ester with alkyl and aryl isothiocyanates
under mild conditions resulted in the corresponding thiohydantoin-fused tetrahydro-β-carbolines. Treatment of the ethyl ester
with isocyanates furnished ethyl 2-alkyl- or arylcarbamoyl-1,2,3,4-tetrahydro-β-carboline-1-carboxylates which were transformed
to hydantoin-fused tetrahydro-β-carbolines. The structures of the thiohydantoin compounds, involving two conformers and the
presence of keto-enol tautomerism, were determined by NMR spectroscopy.
Corresponding author. E-mail: fulop@pharma.szote.u-szeged.hu
Received February 2, 2002. Accepted (revised) March 4, 2002 相似文献
13.
Siavosh Mahboobi Markus Koller Dieter Schollmeyer 《Monatshefte für Chemie / Chemical Monthly》2000,131(4):383-392
Summary. The racemates of the rubiacea alkaloid Chrysotricine (1) and its diastereomer are synthesized from the isomeric mixture of linalyl oxides 3 and tryptamine in six steps, followed by separation of the diastereomers.
Received November 11, 1999. Accepted November 25, 1999 相似文献
14.
Summary. Starting from 2-anilino-2-ethoxy-3-oxothiobutyric acid anilides and (R, R)-or (S, S)-trans-1,2-diaminocyclohexane, chiral C2-disubstituted perhydrobenzimidazole and trans-4a,5,6,7,8,8a-hexahydroquinoxaline derivatives were obtained depending on the polarity of the solvent.
Received April 10, 2000. Accepted May 2, 2000 相似文献
15.
Jan Zawadiak Mirosław Danch Mariola Pigulla 《Monatshefte für Chemie / Chemical Monthly》2001,132(7):821-824
Summary. Syntheses of novel primary-tertiary bisperoxides were carried out under phase transfer catalysis conditions. The bisperoxides
were obtained in good yields, the reaction times not exceeding four hours.
Received January 15, 2001. Accepted (revised) February 9, 2001 相似文献
16.
Süleyman Gürsoy Zehra A. Bayır Esin Hamuryudan Özer Bekarogğlu 《Monatshefte für Chemie / Chemical Monthly》2000,131(3):287-292
Summary. Unsymmetric metallophthalocyanines (M=Zn, Co, Ni) carrying alkylthio and acetyloxyethylthio groups on peripheral positions were prepared from 4,5-bis-alkylthio-phthalonitrile, 4,5-bis-(acetyloxyethylthio)-phthalonitrile, and the corresponding anhydrous metal salts Zn(CH3COO)2, NiCl2, and CoCl2. The extremely soluble compounds were characterized by their IR, 1H NMR, and UV/Vis spectra. Their long wavelength absorption band was found to be bathochromically shifted; their solubility
is superior to that of symmetrical phthalocyanines.
Received July 27, 1999. Accepted (revised) September 30, 1999 相似文献
17.
Ulrich Englich Ingo Prass Karin Ruhlandt-Senge Thorsten Schollmeier Frank Uhlig 《Monatshefte für Chemie / Chemical Monthly》2002,133(7):931-943
Summary. Hydrido substituted stannasilanes of the type or (Z = H, Me, Ph; R, R′ = alkyl, Ph) are accessible by reaction of either alkali metal stannides (MSn(Z)R
2; M = Li, Na) with halogen substituted silanes (; X = F, Cl) or chlorostannanes (R
2SnCl2, Ph3SnCl) and fluorosilanes in the presence of magnesium. Stannasilanes with halogen substituents at the silicon as well as the tin atom are formed by
treatment of the hydrido substituted stannasilanes with CHCl3 or CCl4. The hydrido substituted stannasilanes decompose in contact with air to distannanes and siloxanes or to the linear (
t
Bu2Sn(–O–
t
Bu2Si–OH)2) and cyclic ((–
t
Bu2Sn–O–
i
Pr2Si–O–)2) stannasiloxanes.
Received November 29, 2001. Accepted (revised) January 16, 2002 相似文献
18.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(47):15188-15192
The first example of base‐metal‐catalysed synthesis of amides from the coupling of primary amines with either alcohols or esters is reported. The reactions are catalysed by a new manganese pincer complex and generate hydrogen gas as the sole byproduct, thus making the overall process atom‐economical and sustainable. 相似文献
19.
Konstantinos Kordatos Tatiana Da Ros Maurizio Prato Chuping Luo Dirk Guldi 《Monatshefte für Chemie / Chemical Monthly》2001,132(1):63-69
Summary. Fullerene derivatives exhibit absorption throughout the UV/Vis region up to 750 nm. This feature is important for easy excitation.
Once excited, fullerenes may become both electron and energy acceptors. The distinction between these two pathways depends
strongly on the partner involved (donor) and on the conditions employed (solvent, etc.).
Received June 23, 2000. Accepted July 7, 2000 相似文献
20.
Rita Skoda-Földes Laura Bánffy Judit Horváth Zoltán Tuba László Kollár 《Monatshefte für Chemie / Chemical Monthly》2000,131(12):1363-1369
Summary. The synthesis of novel 3- and 17-diphenylphosphino-androstane derivatives via homogeneous catalytic P-C coupling is described. The products were characterized by 1H and 31P NMR measurements. According to the NMR investigation of the PtCl2P2-type complexes, the steroidal phosphines are trans-coordinated with respect to the Pt-centre exclusively.
Received June 14, 2000. Accepted (revised) July 24, 2000 相似文献