104898-06-8Relevant academic research and scientific papers
Catalytic activity and recyclability of new enantioselective chiral Co-salen complexes in the hydrolytic kinetic resolution of epichlorohydrine
Kim, Geon-Joong,Lee, Hosung,Kim, Seong-Jin
, p. 5005 - 5008 (2003)
Chiral Co(III) salen catalysts bearing PF6, BF4 or Br counterions proved to be reactive and enantioselective in the hydrolytic resolution of terminal epoxides. The catalysts could be recovered and reused several times without further
Mechanistic basis for high stereoselectivity and broad substrate scope in the (salen)Co(III)-catalyzed hydrolytic kinetic resolution
Ford, David D.,Nielsen, Lars P. C.,Zuend, Stephan J.,Musgrave, Charles B.,Jacobsen, Eric N.
, p. 15595 - 15608 (2013)
In the (salen)Co(III)-catalyzed hydrolytic kinetic resolution (HKR) of terminal epoxides, the rate- and stereoselectivity-determining epoxide ring-opening step occurs by a cooperative bimetallic mechanism with one Co(III) complex acting as a Lewis acid and another serving to deliver the hydroxide nucleophile. In this paper, we analyze the basis for the extraordinarily high stereoselectivity and broad substrate scope observed in the HKR. We demonstrate that the stereochemistry of each of the two (salen)Co(III) complexes in the rate-determining transition structure is important for productive catalysis: a measurable rate of hydrolysis occurs only if the absolute stereochemistry of each of these (salen)Co(III) complexes is the same. Experimental and computational studies provide strong evidence that stereochemical communication in the HKR is mediated by the stepped conformation of the salen ligand, and not the shape of the chiral diamine backbone of the ligand. A detailed computational analysis reveals that the epoxide binds the Lewis acidic Co(III) complex in a well-defined geometry imposed by stereoelectronic rather than steric effects. This insight serves as the basis of a complete stereochemical and transition structure model that sheds light on the reasons for the broad substrate generality of the HKR.
Enzyme Assisted Synthesis of Enantiomerically Pure δ-Lactones
Haase, Bernhard,Schneider, Manfred P.
, p. 1017 - 1026 (1993)
Both enantiomers series of a wide variety of optically pure 6-alkylated δ-lactones - saturated as well as unsaturated - were prepared via an enzyme mediated route.The key reaction step is the nucleophilic ring opening of enantiomerically pure alkyl-oxiranes, accessible via the corresponding β-hydroxythioesters which can be obtained enantiomerically pure via enzyme catalyzed kinetic resolutions.
Stereospecific Epitaxial Growth of Bilayered Porous Molecular Networks
Fang, Yuan,Lindner, Benjamin D.,Destoop, Iris,Tsuji, Takashi,Zhang, Zhenzhe,Khaliullin, Rustam Z.,Perepichka, Dmitrii F.,Tahara, Kazukuni,Feyter, Steven De,Tobe, Yoshito
, p. 8662 - 8671 (2020)
Stereocontrolled multilayer growth of supramolecular porous networks at the interface between graphite and a solution was investigated. For this study, we designed a chiral dehydrobenzo[12]annulene (DBA) building block bearing alkoxy chains substituted at the 2 position with hydroxy groups, which enable van der Waals stabilization in a layer and potential hydrogen-bonding interactions between the layers. Bias voltage-dependent scanning tunneling microscopy (STM) experiments revealed the diastereospecificity of the bilayer with respect to both the intrinsic chirality of the building blocks and the supramolecular chirality of the self-assembled networks. Top and bottom layers within the same crystalline domain were composed of the same enantiomers but displayed opposite supramolecular chiralities.
Tailoring the window sizes to control the local concentration and activity of (salen)Co catalysts in plugged nanochannels of SBA-15 materials
Shakeri, Mozaffar,Klein Gebbink, Robertus J. M.,De Jongh, Petra E.,De Jong, Krijn P.
, p. 10854 - 10857 (2013)
Ship shape! Chiral (salen)CoIII complexes (spheres) inside plugged nanochannels of SBA-15 materials is achieved using a ship-in-a-bottle synthesis technique. The local concentration of the metal complexes and the catalytic activity (such as the hydrolytic kinetic resolution of 1,2-epoxyalkanes; see scheme) showed a strong dependence on the size of the window. Copyright
Fluorous biphasic hydrolytic kinetic resolution of terminal epoxides
Shepperson, Ian,Cavazzini, Marco,Pozzi, Gianluca,Quici, Silvio
, p. 175 - 180 (2004)
Although application of light-fluorous techniques facilitates the isolation of reaction products from the hydrolytic kinetic resolution (HKR) of terminal epoxides catalysed by cobalt complexes of salen ligands, the extension of the original fluorous biphasic approach to this reaction is far from being a trivial exercise. The nature of the counter anion has a dramatic effect on the catalytic activity of heavily fluorinated chiral (salen) cobalt(III) complexes. Excellent enantioselectivities are obtained in the fluorous biphasic HKR of 1,2-hexene oxide when fluorinated anions are introduced (e.e.s up to 99% both for the diol and the epoxide), with C8F17COO- affording reaction rates even higher than those observed with non-fluorous systems.
Enantioselective epoxidation of terminal alkenes to (R)- and (S)-epoxides by engineered cytochromes P450 BM-3
Kubo, Takafumi,Peters, Matthew W.,Meinhold, Peter,Arnold, Frances H.
, p. 1216 - 1220 (2006)
Cytochrome P450 BM-3 from Bacillus megaterium was engineered for enantioselective epoxidation of simple terminal alkenes. Screening saturation mutagenesis libraries, in which mutations were introduced in the active site of an engineered P450, followed by recombination of beneficial mutations generated two P450 BM-3 variants that convert a range of terminal alkenes to either (R)- or (S)epoxidc (up to 83 % ee) with high catalytic turnovers (up to 1370) and high epoxidation selectivities (up to 95%). A biocatalytic system using E. coli lysates containing P450 variants as the epoxidation catalysts and in vitro NADPH regeneration by the alcohol dehydrogenase from Thermoanaerobium brockii generates each of the epoxide enantiomers, without additional cofactor.
CrIII(salen) impregnated on silica for asymmetric ring opening reactions and its recovery via desorption/re-impregnation
Dioos, Bart M. L.,Jacobs, Pierre A.
, p. 8815 - 8817 (2003)
The impregnation of CrIII(salen) complexes on silica resulted in a heterogeneous catalyst for the asymmetric ring opening (ARO) reaction of epoxides with good selectivity and acceptable activity. As became apparent from a series of 10 successive batch tests in the ARO reaction of 1,2-epoxyhexane, leaching was limited, while catalytic activity and selectivity were acceptable. Though the support suffered from abrasion in the batch reactor, 80% of the catalyst was easily recoverable via simple extraction from the used solid catalyst and entirely transferable onto a fresh carrier via impregnation. It was shown that 80% of the leached catalyst at the end of the tests could be transformed into a fresh heterogeneous catalyst as well.
Spiroacetal biosynthesis: (±)-1,7-dioxaspiro[5.5]undecane in Bactrocera cacuminata and Bactrocera oleae (olive fruit fly)
Schwartz, Brett D.,McErlean, Christopher S. P.,Fletcher, Mary T.,Mazomenos, Basilis E.,Konstantopoulou, Maria A.,Kitching, William,De Voss, James J.
, p. 1173 - 1176 (2005)
A biosynthetic scheme rationalizing the formation of (±)-1,7- dioxaspiro[5.5]undecane (5) in the fruit fly species Bactrocera cacuminata and Bactrocera oleae (olive fruit fly) is presented. Incorporation studies with deuterium-labeled keto aldehyde (10), 1,5-nonanediol (11), and 1,5,9-nonanetriol (12), and our previous finding that both oxygen atoms of 5 originate from dioxygen, are strongly evidentiary. The racemic condition of the natural spiroacetal 5 is accounted for, and inter alia, it is demonstrated that dihydropyran (18) is not an important intermediate en route to 5.
Application of homochiral alkylated organic cages as chiral stationary phases for molecular separations by capillary gas chromatography
Xie, Shengming,Zhang, Junhui,Fu, Nan,Wang, Bangjin,Hu, Cong,Yuan, Liming
, (2016)
Molecular organic cage compounds have attracted considerable attention due to their potential applications in gas storage, catalysis, chemical sensing, molecular separations, etc. In this study, a homochiral pentyl cage compound was synthesized from a condensation reaction of (S,S)-1,2-pentyl-1,2-diaminoethane and 1,3,5-triformylbenzene. The imine-linked pentyl cage diluted with a polysiloxane (OV-1701) was explored as a novel stationary phase for high-resolution gas chromatographic separation of organic compounds. Some positional isomers were baseline separated on the pentyl cage-coated capillary column. In particular, various types of enantiomers including chiral alcohols, esters, ethers and epoxides can be resolved without derivatization on the pentyl cage-coated capillary column. The reproducibility of the pentyl cage-coated capillary column for separation was investigated using nitrochlorobenzene and styrene oxide as analytes. The results indicate that the column has good stability and separation reproducibility after being repeatedly used. This work demonstrates that molecular organic cage compounds could become a novel class of chiral separation media in the near future.
