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Asymmetric Reduction of C=N Bonds by Imine Reductases and Reductive Aminases
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Matthias Höhne, Philipp Matzel, Martin Gand
Imine reduction is taking place in several pathways: Δ1-pyrroline-2-carboxylate reductases convert cyclic imine substrates bearing a carboxylate function attached to the imine carbon atom and produce l-proline 6 or its six-membered ring analogue l-pipecolic acid 8 (Goto et al., 2005), an intermediate involved in lysine metabolism (Table 14.1, entry 1). Note that two reductases exist that convert substrates with the carboxylate attached either at the imine carbon atom (1-pyrroline-2-carboxylate 5), or at position 5 in the ring (1-pyrroline-5-carboxylate 7). In the latter case, reduction of 7 also leads to l-proline, but the stereo center is already present in the substrate and it is not created during imine reduction in this case (Nocek et al., 2005) (Fig. 14.6). Thiomorpholine-carboxylate dehydrogenase catalyzes a similar reaction (Table 14.1, entry 2) and also converts sulfur-containing proline- and pipecolic acid derivatives 25–27. Two reductases leading to l-proline formation.
Physical Constants of Organic Compounds
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
1,2-Dihydro-3,6-pyridazinedi- Maleic hydrazide one Dihydro-2,4(1H,3H)-pyrimidin- 5,6-Dihydrouracil edione 2,5-Dihydro-1H-pyrrole 3-Pyrroline 3,4-Dihydro-2(1H)-quinolinone Hydrocarbostyril 1,4-Dihydro-2,3-quinoxaline- 2,3-Quinoxalinediol dione Dihydrotachysterol Dihydrothebaine 4,5-Dihydro-2-thiazolamine 2,3-Dihydrothiophene 2,5-Dihydrothiophene 2,5-Dihydrothiophene 1,1-dioxide Dihydro-2(3H)-thiophenone Dihydro-2-thioxo-4,6(1H,5H)pyrimidinedione 2,3-Dihydro-2-thioxo-4(1H)pyrimidinone 1,2-Dihydro-3H-1,2,4triazole-3-thione (1,3-Dihydro-1,3,3-trimethyl2H-indol-2-ylidene) acetaldehyde 2,3-Dihydro-1,1,3-trimethyl3-phenyl-1H-indene 1,2-Dihydro-2,2,4-trimethylquinoline 1,4-Dihydroxy-9,10-anthracenedione 1,5-Dihydroxy-9,10-anthracenedione 1,8-Dihydroxy-9,10-anthracenedione 2,6-Dihydroxy-9,10-anthracenedione 2,7-Dihydroxy-9,10-anthracenedione
Five-Membered Fused Polyheterocycles
Published in Navjeet Kaur, Metals and Non-Metals, 2020
5-Stannylated N-Boc-protected 2,3-dihydro-1H-pyrrole can be prepared by direct lithiation-stannylation of N-Boc-pyrroline and is used in Stille cross-coupling with vinyl triflate to afford trienecarbarbamate. This compound is heated to affect an electrocyclic ring-closure and oxidized in situ with MnO2 to afford the marine sponge metabolite (±)-cis-trikentrin A after Boc-de-protection and aromatization (Scheme 28). (±)-cis-trikentrin B is synthesized from a related stannylated pyrroline as the starting compound [71–72].
Semiexperimental equilibrium structure of 1-methylisatin from gas-phase electron diffraction data and structural changes in isatin due to 1-methyl and 5-fluoro substituents as predicted by coupled cluster computations
Published in Molecular Physics, 2019
Alexander V. Belyakov, Kirill O. Nikolaenko, Alexander A. Oskorbin, Natalja Vogt, Anatolii N. Rykov, Igor F. Shishkov
For the first time, the molecular structure of 1-methylisatin is studied by an experimental method in the gas phase. The high accuracy of the semiexperimental equilibrium structure, determined from gas-phase electron diffraction data taking into account anharmonic vibrational effects, allows the benchmarking of the results of quantum chemical computations (up to CCSD(T)_AE/wCVQZ quality). Furthermore, the high accuracy of the computed structures of isatin and its 1-methyl and 5-fluoro derivatives makes possible the revealing of fine structural effects comparable in magnitude with experimental uncertainty. The electron donating methyl group causes a decrease of the C−N−C angle and an elongation of the N−C bond lengths in the pyrroline ring by 0.7° and by up to 0.008 Å, whereas the electron withdrawing fluorine substituent increases the ipso CCC angle by 2.5° in respect to that in unsubstituted isatin.
Pulse EPR distance measurements to study multimers and multimerisation
Published in Molecular Physics, 2018
Katrin Ackermann, Bela E. Bode
For PELDOR, the most commonly used spin labels for SDSL are stable nitroxide radicals such as MTSL ((1 - oxyl - 2,2,5,5 - tetramethyl - δ3 - pyrroline-3-methyl) methanethiosulfonate) [7,23]. However, paramagnetic metal ions that can be used in combination with systems bearing a native or introduced metal-binding site are receiving increasing attention [24–27]. These labels are more stable than nitroxides in the reducing environment of the cell [28,29], and are especially attractive in combination with evolving methodology, such as shaped pulses [30,31] or RIDME (relaxation-induced dipolar modulation enhancement) [32], to compensate for the reduced overall modulation depth Δ achievable with metal ions compared to nitroxides. Compared to PELDOR, fast relaxation times and broad spectra (as observed in metal ions) can be less problematic using RIDME. While PELDOR is by far the more established and better understood technique, RIDME has great potential, and recent advances, such as the dead-time free five-pulse version [33], averaging schemes to reduce nuclear modulation artefacts [34], or modified Tikhonov kernels to eliminate overtones [35], will significantly widen the scope of this method.