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Search for "kinetic isotope effect" in Full Text gives 30 result(s) in Beilstein Journal of Organic Chemistry.
[2H26]-1-epi-Cubenol, a completely deuterated natural product from Streptomyces griseus
- Christian A. Citron and
- Jeroen S. Dickschat
Beilstein J. Org. Chem. 2013, 9, 2841–2845, doi:10.3762/bjoc.9.319
- Streptomyces griseus. This compound represents the first completely deuterated terpene obtained by fermentation. Despite a few previous reports in the literature the operability of this approach to fully deuterated compounds is still surprising, because the strong kinetic isotope effect of deuterium is known
- eight to ten days of incubation until fully grown, reflecting the significantly slowed metabolism due to a strong deuterium kinetic isotope effect. After full growth of the culture the volatiles emitted by S. griseus were collected on charcoal traps by use of a closed-loop stripping apparatus (CLSA) [25
Graphical Abstract
Figure 1: Terpenoids from Streptomyces griseus.
Figure 2: Total ion chromatograms of CLSA headspace extracts from S. griseus obtained after (A) incubation on...
Figure 3: Mass spectra of 1-epi-cubenol. (A) Mass spectrum of natural 3 obtained after growth on 65.GYM; (B) ...
Figure 4: Ion chromatograms of fully deuterated 3 for (A) the molecular ion (m/z = 248, 247, and 246), and (B...
Recent advances in transition metal-catalyzed Csp2-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation
- Grégory Landelle,
- Armen Panossian,
- Sergiy Pazenok,
- Jean-Pierre Vors and
- Frédéric R. Leroux
Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287
- induction period and demonstrated the involvement of radical species in the reaction. The authors proposed a mechanism accounting for the EPR profile of the reaction and for the results of kinetic isotope effect experiments (Figure 21). In this mechanism, rhenium intervenes in the initiation step. It acts
Graphical Abstract
Scheme 1: Pd-catalyzed monofluoromethylation of pinacol phenylboronate [44].
Scheme 2: Cu-catalyzed monofluoromethylation with 2-PySO2CHFCOR followed by desulfonylation [49].
Scheme 3: Cu-catalyzed difluoromethylation with α-silyldifluoroacetates [57].
Figure 1: Mechanism of the Cu-catalyzed C–CHF2 bond formation of α,β-unsaturated carboxylic acids through dec...
Scheme 4: Fe-catalyzed decarboxylative difluoromethylation of cinnamic acids [62].
Scheme 5: Preliminary experiments for investigation of the mechanism of the C–H trifluoromethylation of N-ary...
Figure 2: Plausible catalytic cycle proposed by Z.-J. Shi et al. for the trifluoromethylation of acetanilides ...
Figure 3: Plausible catalytic cycle proposed by M. S. Sanford et al. for the perfluoroalkylation of simple ar...
Figure 4: Postulated reaction pathway for the Ag/Cu-catalyzed trifluoromethylation of aryl iodides by Z. Q. W...
Figure 5: Postulated reaction mechanism for Cu-catalyzed trifluoromethylation reaction using MTFA as trifluor...
Scheme 6: Formal Heck-type trifluoromethylation of vinyl(het)arenes by M. Sodeoka et al. [83].
Figure 6: Proposed catalytic cycle for the copper-catalyzed trifluoromethylation of (het)arenes in presence o...
Figure 7: Proposed catalytic cycle for the copper-catalyzed trifluoromethylation of N,N-disubstituted (hetero...
Figure 8: Proposed catalytic cycle by Y. Zhang and J. Wang et al. for the copper-catalyzed trifluoromethylati...
Figure 9: Mechanistic rationale for the trifluoromethylation of arenes in presence of Langlois’s reagent and ...
Scheme 7: Trifluoromethylation of 4-acetylpyridine with Langlois’s reagent by P. S. Baran et al. (* Stirring ...
Scheme 8: Catalytic copper-facilitated perfluorobutylation of benzene with C4F9I and benzoyl peroxide [90].
Figure 10: F.-L. Qing et al.’s proposed mechanism for the copper-catalyzed trifluoromethylation of (hetero)are...
Figure 11: Mechanism of the Cu-catalyzed/Ru-photocatalyzed trifluoromethylation and perfluoroalkylation of ary...
Figure 12: Proposed mechanism for the Cu-catalyzed trifluoromethylation of aryl- and vinyl boronic acids with ...
Figure 13: Possible mechanism for the Cu-catalyzed decarboxylative trifluoromethylation of cinnamic acids [62].
Scheme 9: Ruthenium-catalyzed perfluoroalkylation of alkenes and (hetero)arenes with perfluoroalkylsulfonyl c...
Figure 14: N. Kamigata et al.’s proposed mechanism for the Ru-catalyzed perfluoroalkylation of alkenes and (he...
Figure 15: Proposed mechanism for the Ru-catalyzed photoredox trifluoromethylation of (hetero)arenes with trif...
Figure 16: Late-stage trifluoromethylation of pharmaceutically relevant molecules with trifluoromethanesulfony...
Figure 17: Proposed mechanism for the trifluoromethylation of alkenes with trifluoromethyl iodide under Ru-bas...
Scheme 10: Formal perfluoroakylation of terminal alkenes by Ru-catalyzed cross-metathesis with perfluoroalkyle...
Figure 18: One-pot Ir-catalyzed borylation/Cu-catalyzed trifluoromethylation of complex small molecules by Q. ...
Figure 19: Mechanistic proposal for the Ni-catalyzed perfluoroalkylation of arenes and heteroarenes with perfl...
Scheme 11: Electrochemical Ni-catalyzed perfluoroalkylation of 2-phenylpyridine (Y. H. Budnikova et al.) [71].
Scheme 12: Fe(II)-catalyzed trifluoromethylation of arenes and heteroarenes with trifluoromethyl iodide (T. Ya...
Figure 20: Mechanistic proposal by T. Yamakawa et al. for the Fe(II)-catalyzed trifluoromethylation of arenes ...
Scheme 13: Ytterbium-catalyzed perfluoroalkylation of dihydropyran with perfluoroalkyl iodide (Y. Ding et al.) ...
Figure 21: Mechanistic proposal by A. Togni et al. for the rhenium-catalyzed trifluoromethylation of arenes an...
Figure 22: Mechanism of the Cu-catalyzed oxidative trifluoromethylthiolation of arylboronic acids with TMSCF3 ...
Scheme 14: Removal of the 8-aminoquinoline auxiliary [136].
Figure 23: Mechanism of the Cu-catalyzed trifluoromethylthiolation of C–H bonds with a trifluoromethanesulfony...
The role of silver additives in gold-mediated C–H functionalisation
- Scott R. Patrick,
- Ine I. F. Boogaerts,
- Sylvain Gaillard,
- Alexandra M. Z. Slawin and
- Steven P. Nolan
Beilstein J. Org. Chem. 2011, 7, 892–896, doi:10.3762/bjoc.7.102
- (Scheme 2) [16]. The observation of a high kinetic isotope effect is suggestive of a concerted metalation–deprotonation mechanism, as first suggested for Pd(II) complexes, in which a pivalate ligand behaves as a proton acceptor via a six-membered transition state [17]. However, addition via a transient Au
Graphical Abstract
Scheme 1: Silver-free C–H functionalisation using [Au(OH)(IPr)].
Scheme 2: C–H functionalisation of 2 using gold-phosphine complexes and a silver additive.
Figure 1: X-ray structure of [Au(OPiv)(IPr)] 3. Thermal ellipsoids are shown at the 50% probability level. H ...
Scheme 3: Carboxylation of 2 using 1 and Ag2O.
Catalysis: transition-state molecular recognition?
- Ian H. Williams
Beilstein J. Org. Chem. 2010, 6, 1026–1034, doi:10.3762/bjoc.6.117
- an archetypal reaction in organic chemistry and an important process in biochemistry. Catechol-O-methyl transferase (COMT) catalyses methyl transfer from S-adenosylmethionine (SAM) to a catechol (Scheme 1), and this reaction manifests an unusually large inverse secondary kinetic isotope effect as
Graphical Abstract
Figure 1: Free energy profiles for reactions of substrate S uncatalysed and catalysed by enzyme E, showing ho...
Scheme 1: SN2 methyl transfer from SAM to catechol catalysed by COMT.
Figure 2: Energetic analysis of the compression hypothesis for enzyme-catalysed methyl transfer.
Figure 3: Catalyst design for methyl transfer: (a) the reaction to be catalysed; (b) dipoles favourably align...
Scheme 2: SN2 methyl transfer (a) uncatalysed and (b) within a cryptand cavity.
Figure 4: Free energy analysis of COMT catalysis.
Scheme 3: Formation of glycosyl-enzyme covalent intermediate COV.
Figure 5: Conformational change of the xylose ring from chair (via envelope) with long OYHY…Oring hydrogen bo...
Figure 6: AM1/OPLS potentials of mean force for formation of glycosyl-enzyme covalent intermediate between 4-...
Figure 7: Hydrogen-bond distances HY…Oring (red) and HY…Onuc (blue) to boat conformer of RC, TS and glycosyl-...
Mitomycins syntheses: a recent update
- Jean-Christophe Andrez
Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33
- . They rationalized that monodeuterio derivative 109 should be a better substrate, having a slower indole deprotonation rate, due to a primary kinetic isotope effect. Accordingly, treatment of the monodeuterio derivative 109 with methyl lithium followed by quenching with phenylselenium chloride yielded
Graphical Abstract
Scheme 1: Aziridine containing natural products.
Scheme 2: Mitomycin structures and nomenclature.
Scheme 3: Base catalysed epimerization of mitomycin B.
Scheme 4: Biosynthesis of mitomycin C (MMC) 7.
Scheme 5: Mode of action of mitomycin C.
Scheme 6: The N–C3–C9a disconnection.
Scheme 7: Danishefsky’s Retrosynthesis of mitomycin K.
Scheme 8: Hetero Diels–Alder reaction en route to mitomycins.
Scheme 9: Nitroso Diels–Alder cycloaddition.
Scheme 10: Frank azide cycloadddition.
Scheme 11: Final steps of mitomycin K synthesis. aPDC, DCM; bPhSCH2N3, PhH, 80 °C; cL-selectride, THF, −78 °C; ...
Scheme 12: Naruta–Maruyama retrosynthesis.
Scheme 13: Synthesis of a leucoaziridinomitosane by nitrene cycloaddition. aAlCl3-Et2O; bNaH, ClCH2OMe; cn-BuL...
Scheme 14: Thermal decomposition of azidoquinone 51.
Scheme 15: Diastereoselectivity during the cycloaddition.
Scheme 16: Oxidation with iodo-azide.
Scheme 17: Williams’ approach towards mitomycins.aDEIPSCl, Imidazole, DCM; bPd/C, HCO2NH4, MeOH; cAllocCl, NaH...
Scheme 18: Synthesis of pyrrolidones by homoconjugate addition.
Scheme 19: Homoconjugate addition on the fully functionalized substrate.
Scheme 20: Introduction of the olefin.
Scheme 21: Retrosynthesis of N–C9a, N–C3 bond formation.
Scheme 22: Synthesis of the pyrrolo[1,2]indole 82 using N-PSP activation.aAc2O, Py; bAc2O, Hg(OAc)2, AcOH, 90%...
Scheme 23: Synthesis of an aziridinomitosane. am-CPBA, DCM then iPr2NH, CCl4 reflux; bK2CO3, MeOH; cBnBr, KH; d...
Scheme 24: Oxidation products of a leucoaziridinomitosane obtained from a Polonovski oxidation.
Scheme 25: Polonovski oxidation of an aziridinomitosane. am-CPBA; bPd/C, H2; cDimethoxypropane, PPTS.
Scheme 26: The C1–C9a disconnection.
Scheme 27: Ziegler synthesis of desmethoxymitomycin A.aIm2C=O, THF; bNH3; cTMSOTf, 2,6-di-tert-butylpyridine, ...
Scheme 28: Transformation of sodium erythorbate.aTBDMSCl; bNaN3; cPPh3; d(Boc)2O, DMAP; eTBAF; fTf2O, Pyr.
Scheme 29: Formation of C9,C10-unsaturation in the mitomycins. am-CPBA, DCM; bO3, MeOH; cMe2S; dKHMDS, (EtO)3P...
Scheme 30: Fragmentation mechanism.
Scheme 31: Michael addition-cyclisation.
Scheme 32: SmI2 8-endo-dig cyclisation.
Scheme 33: Synthesis of pyrrolo[1,2-a]indole by 5-exo-dig radical cyclization.
Scheme 34: The C9–C9a disconnection.
Scheme 35: Intramolecular nitrile oxide cycloaddition.
Scheme 36: Regioselectivity of the INOC.
Scheme 37: Fukuyama’s INOC strategy.
Scheme 38: Synthesis of a mitosane core by rearrangement of a 1-(1-pyrrolidinyl)-1,3-butadiene.
Scheme 39: Sulikowski synthesis of an aziridinomitosene. aPd(Tol3P)2Cl2, Bu3SnF, 140; bH2, Pd/C; cTFAA, Et3N; d...
Scheme 40: Enantioselective carbene insertion.
Scheme 41: Parson’s radical cyclization.
Scheme 42: Cha’s mitomycin B core synthesis.
Scheme 43: The N-aromatic disconnection.
Scheme 44: Kishi retrosynthesis.
Scheme 45: Kishi synthesis of a starting material. aallyl bromide, K2CO3, acetone, reflux; bN,N-Dimethylanilin...
Scheme 46: Kishi synthesis of MMC 7. aLDA, THF, −78 °C then PhSeBr, THF, −78 °C; bH2O2, THF-EtOAc; cDIBAL, DCM...
Scheme 47: Acid catalyzed degradation of MMC 7.
Scheme 48: In vivo formation of apomitomycin B.
Scheme 49: Advanced intermediate for apomitomycin B synthesis.
Scheme 50: Remers synthesis of a functionalized mitosene. aTMSCl, Et3N, ZnCl2 then NBS; bAcOK; cNH2OH; dPd/C, H...
Scheme 51: Coleman synthesis of desmethoxymitomycin A. aSnCl2, PhSH, Et3N, CH3CN; bClCO2Bn, Et3N; cPPh3, DIAD,...
Scheme 52: Transition state and pyrrolidine synthesis.
Scheme 53: Air oxidation of mitosanes and aziridinomitosanes.
Scheme 54: The C9-aromatic disconnection.
Scheme 55: Synthesis of the aziridine precursor. aLHMDS, THF; bNaOH; c(s)-α-Me-BnNH2, DCC, HOBT; dDIBAL; eK2CO3...
Scheme 56: Synthesis of 206 via enamine conjugate addition.
Scheme 57: Rapoport synthesis of an aziridinomitosene.
Scheme 58: One pot synthesis of a mitomycin analog.
Scheme 59: Synthesis of compound 218 via intramolecular Heck coupling. aEtMgCl, THF, then 220; bMsCl, Et3N; cN...
Scheme 60: Elaboration of indole 223. aEt3N, Ac2O; bAcOH; cSOCl2, Et3N; dNaN3, DMF; eH2SO4, THF; fK2CO3, MeOH; ...
Scheme 61: C9-C9a functionalization from indole.
Scheme 62: Synthesis of mitomycin K. a2 equiv. MoO5.HMPA, MeOH; bPPh3, Et3N, THF-H2O; cMeOTf, Py, DCM; dMe3SiCH...
Scheme 63: Configurational stability of mitomycin K derivatives.
Scheme 64: Epimerization of carbon C9a in compound 227b.
Scheme 65: Corey–Chaykovsky synthesis of indol 235.
Scheme 66: Cory intramolecular aza-Darzens reaction for the formation of aziridinomitosene 239.
Scheme 67: Jimenez synthesis of aziridinomitosene 242.
Scheme 68: Von Braun opening of indoline 244.
Scheme 69: C9a oxidation of an aziridinomitosane with DDQ/OsO4.
Scheme 70: Synthesis of epi-mitomycin K. aNaH, Me2SO4; bH2, Pd/C; cMitscher reagent [165]; d[(trimethylsilyl)methyl...
Scheme 71: Mitomycins rearrangement.
Scheme 72: Fukuyama’s retrosynthesis.
Scheme 73: [2+3] Cycloaddition en route to isomitomycin A. aToluene, 110 °C; bDIBAL, THF, −78 °C; cAc2O, Py.; d...
Scheme 74: Final steps of Fukuyama’s synthesis.
Scheme 75: “Crisscross annulation”.
Scheme 76: Synthesis of 274; the 8-membered ring 274 was made using a crisscross annulation. a20% Pd(OH)2/C, H2...
Scheme 77: Conformational analysis of compound 273 and 275.
Scheme 78: Synthesis of a mitomycin analog. aNa2S2O4, H2O, DCM; bBnBr (10 equiv), K2CO3, 18-crown-6 (cat.), TH...
Scheme 79: Vedejs retrosynthesis.
Scheme 80: Formation of the azomethine ylide.
Scheme 81: Vedejs second synthesis of an aziridinomitosene. aDIBAL; bTPAP, NMO; c287; dTBSCl, imidazole.
Scheme 82: Trityl deprotection and new aziridine protecting group 300.
Scheme 83: Ene reaction towards benzazocinones.
Scheme 84: Benzazocenols via homo-Brook rearrangement.
Scheme 85: Pt-catalyzed [3+2] cycloaddition.
Scheme 86: Carbonylative lactamization entry to benzazocenols. aZn(OTf)2, (+)-N-methylephedrine, Et3N, TMS-ace...
Scheme 87: 8 membered ring formation by RCM. aBOC2O, NaHCO3; bTBSCl, Imidazole, DMF; callyl bromide, NaH, DMF; ...
Scheme 88: Aziridinomitosene synthesis. aTMSN3; bTFA; cPOCl3, DMF; dNaClO2, NaH2PO4, 2-methyl-2-butene; eMeI, ...
Scheme 89: Metathesis from an indole.
Scheme 90: Synthesis of early biosynthetic intermediates of mitomycins.
