57680-86-1Relevant academic research and scientific papers
Simultaneous engineering of an enzyme's entrance tunnel and active site: The case of monoamine oxidase MAO-N
Li, Guangyue,Yao, Peiyuan,Gong, Rui,Li, Jinlong,Liu, Pi,Lonsdale, Richard,Wu, Qiaqing,Lin, Jianping,Zhu, Dunming,Reetz, Manfred T.
, p. 4093 - 4099 (2017/07/10)
A new directed evolution approach is presented to enhance the activity of an enzyme and to manipulate stereoselectivity by focusing iterative saturation mutagenesis (ISM) simultaneously on residues lining the entrance tunnel and the binding pocket. This combined mutagenesis strategy was applied successfully to the monoamine oxidase from Aspergillus Niger (MAO-N) in the reaction of sterically demanding substrates which are of interest in the synthesis of chiral pharmaceuticals based on the benzo-piperidine scaffold. Reversal of enantioselectivity of Turner-type deracemization was achieved in the synthesis of (S)-1,2,3,4-tetrahydro-1-methyl-isoquinoline, (S)-1,2,3,4-tetrahydro-1-ethylisoquinoline and (S)-1,2,3,4-tetrahydro-1-isopropylisoquinoline. Extensive molecular dynamics simulations indicate that the altered catalytic profile is due to increased hydrophobicity of the entrance tunnel acting in concert with the altered shape of the binding pocket.
Enhancing effects of salt formation on catalytic activity and enantioselectivity for asymmetric hydrogenation of isoquinolinium salts by dinuclear halide-bridged iridium complexes bearing chiral diphosphine ligands
Kita, Yusuke,Yamaji, Kenta,Higashida, Kosuke,Sathaiah, Kandula,Iimuro, Atuhiro,Mashima, Kazushi
, p. 1915 - 1927 (2015/01/30)
Asymmetric hydrogenation of 1- and 3-substituted and 1,3-disubstituted isoquinolinium chlorides using triply halide-bridged dinuclear iridium complexes [{Ir(H)(diphosphine)} 2(μ -Cl)3]Cl has been achieved by the strategy of HCl salt formation of isoquinolines to afford the corresponding chiral 1,2,3,4-tetrahydroisoquinolines (THIQs) in high yields and with excellent enantioselectivities after simple basic workup. The effects of salt formation have been investigated by time-course experiments, which revealed that the generation of isoquinolinium chlorides clearly prevented formation of the catalytically inactive dinuclear trihydride complex, which was readily generated in the catalytic reduction of salt-free isoquinoline substrates. Based on mechanistic investigations, including by 1H and 31P{1H} NMR studies and the isolation and characterization of several intermediates, the function of the chloride anion of the isoquinolinium chlorides has been elucidated, allowing us to propose a new outer-sphere mechanism involving coordination of the chloride anion of the substrates to an iridium dihydride species along with a hydrogen bond between the chloride ligand and the N-H proton of the substrate salt.
Expanded substrate scope and catalyst optimization for the catalytic kinetic resolution of N-heterocycles
Hsieh, Sheng-Ying,Binanzer, Michael,Kreituss, Imants,Bode, Jeffrey W.
supporting information, p. 8892 - 8894 (2012/11/07)
The scope, reactivity, and selectivity of the chiral hydroxamic acid-catalyzed kinetic resolution of chiral amines are improved by a new catalyst structure and a more environmentally friendly reaction protocol. In addition to increasing selectivity across all substrates, these conditions make possible the resolution of N-heterocycles containing lactams or other basic functional groups that can inhibit the catalyst.
Determination of ring conformation in 1-benzyl-1,2,3,4- tetrahydroisoquinolines and a new synthesis of the chiral compounds
Shinohara, Tatsumi,Takeda, Akira,Toda, Jun,Sano, Takehiro
, p. 430 - 433 (2007/10/03)
The conformation of the piperideine ring in 1-benzyl-1,2,3,4- tetrahydroisoquinolines was determined as 2H3 form with a pseudoaxial position of the 1-benzyl group by circular dichroism (CD) spectral comparison with 1-methyl-1,2,3,4-tetrahydroisoquinolines. The chiral center at C-1 of 1,2,3,4-tetrahydroisoquinoline (TIQ) was constructed in an unambiguous manner by applying a new method of TIQ synthesis utilizing the Pummerer reaction as a key step. Enantiomerically pure (R)- and (S)-1-methyl- and 1- benzyltetrahydroisoquinolines (1) were prepared starting from readily available chiral amines (2) in good overall yields.
New strategies for enantioselective syntheses of 1-alkyl- and 1,4-dialkyl-1,2,3,4-tetrahydroisoquinolines: Diastereoselective additions of nucleophiles and electrophiles to isoquinoline mediated by an easily resolved and recycled chiral transition metal auxiliary
Richter-Addo, George B.,Knight, D. Andrew,Dewey, Michael A.,Arif, Atta M.,Gladysz
, p. 11863 - 11873 (2007/10/02)
The chiral rhenium isoquinoline complex [(η5-C5H5)Re(NO)(PPh 3)(iso-NC9H7)]+ TfO- (1) and (CH3)3-SiCH2Li give the addition product (η5-C5H5)Re(NO)(PPh3)(N?CH = CHC(CH)4CCHCH2Si(CH3)3) (2) in 71% yield as a 94:6 SS,RR/SR,RS diastereomer mixture. Similar reactions with RMgX (R = (CH3)2CH, CH3CH2, C6H5CH2, CH3(CH2)2, CH3, CH3(CH2)3) give analogous adducts (3-8) as 89-82:11-18 diastereomer mixtures. Reactions of 2 and ROTf (R = H/D, (CH3)3SiCH2, CH3) give alkyl-1,4-dihydroisoquinoline complexes [(η5-C5H5)Re(NO)-(PPh3)(N = CHCHRC(CH)4CCHCH2Si(CH3)3)] + TfO- in 84-72% yields as 94:6 diastereomer mixtures. Related complexes are prepared from 3-5 and HOTf. These react with NaBH4/CH3OH to give alkyl-1,2,3,4-tetrahydroisoquinoline complexes, which are in turn treated with (CH3CH2)4N+ CN- to give (η5-C5H5)Re(NO)(PPh3)(CN) (17) and the title compounds. A reaction sequence starting with (+)-(S)-1 and (CH3)3SiCH2Li yields (+)-(SS)-NHCH2-CH(CH2Si(CH3) 3)C(CH)4CCHCH2Si(CH3)3 (84% overall, 88% ee) and (+)-(S)-17 (82%, >98% ee). Other optically active alkyl tetrahydroisoquinolines are similarly prepared. Complexes 17 and (+)-(S)-17 are converted to (η5-C5H5)Re(NO)(PPh3)(CH 3) (CH3OTf/NaBH4; 88-53%) and thence to 1 or (+)-(S)-1 (92-74%, >98% ee). A crystal structure and other data confirm the configurations assigned to the preceding compounds.
Chiral Dipole-Stabilized Anions: Experiment and Theory in Benzylic and Allylic Systems. Stereoselective Deprotonations, Pyramidal Inversions, and Stereoselective Alkylations of Lithiated (Tetrahydroisoquinolyl)oxazolines
Rein, Kathleen,Goicoechea-Pappas, Marta,Anklekar, Tarakeshwar V.,Hart, Georgina C.,Smith, Gregory A.,Gawley, Robert E.
, p. 2211 - 2217 (2007/10/02)
The stereoselective alkylation of chiral (tetrahydroisoquinolyl)oxazolines has been investigated.We report the details of this investigation, including an examination of the effect of both temperature and oxazoline substituent structure on the alkylation diastereoselectivity, a comparison of monodentate vs bidentate chelation of the organolithium, an evaluation of the effect of solvent and chelating solvent additives, the regiochemistry of alkylation of (3,4-dehydropiperidino)oxazolines, lithiation-alkylation experiments on stereoselectively deuterated monodentate and bidentate isoquinolinolyloxazolines, and semiempirical molecular orbital calculations on the organolithium diastereomers 13a,b.There are two distinct stereoselective processes involved in the overall transformation. the proposed mechanism includes an oxazoline-alkyllithium coordination complex that controls the selectivity of the deprotonation step, whereas the selectivity of the electrophilic quench is governed by effects that are as yet undetermined.
