Structure Determination of Organic Compounds

Pretsch, Ernö; Bühlmann, Philippe; Badertscher, Martin

doi:10.1007/978-3-662-04201-4

Cited by 1,817 publications

(735 citation statements)

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“…It is known that the typical coupling constants for the protons in the thiophene ring are: J2,3 (= J4,5) = 4.8 Hz, J2,4 (= J3,5) = 1.0 Hz, J3,4 = 3.5 Hz, and J2,5 = 2.8 Hz. 19 The observed values listed in Table 3 are quite consistent with the typical values. Therefore, the proton signals are readily assigned.…”

Section: Resultssupporting

confidence: 83%

Oxidation of Methylthiophenes to Thiophenecarboxylic Acids

2009

Bulletin of the Korean Chemical Society

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Section: Resultssupporting

confidence: 83%

Oxidation of Methylthiophenes to Thiophenecarboxylic Acids

2009

Bulletin of the Korean Chemical Society

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“…In most cases, the resonance for H15 exo displayed additional long range coupling ( 4 J HH = 1.6 -3.6 Hz), presumeably arising from the W relationship to the axial proton at C14. 35 It is interesting that the altered bond angles resulting from aziridine ring formation in azatrachylobane (13) re-orient H15 endo into position for W-coupling to H14 axial , and consequently the additional coupling appears in the lower field resonance. The W relationship between H15 endo and H14 axial is apparent in the ORTEP in Fig.…”

Section: Proton Nmr Spectramentioning

confidence: 99%

16-Aza-ent-beyerane and 16-Aza-ent-trachylobane: Potent Mechanism-Based Inhibitors of Recombinant ent-Kaurene Synthase from Arabidopsis thaliana

et al. 2007

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The secondary ent-beyeran-16-yl carbocation (7) is a key branch point intermediate in mechanistic schemes to rationalize the cyclic structures of many tetra-and pentacyclic diterpenes including ent-beyerene, ent-kaurene, ent-trachylobane, and ent-atiserene, presumed precursors to > 1,000 known diterpenes. (Scheme 1) To evaluate these mechanistic hypotheses, we synthesized the heterocyclic analogues, 16-aza-ent-beyerane (12) and 16-aza-ent-trachylobane (13), by means of Hg(II)-and Pb(IV)-induced cyclizations onto the Δ 12 double bonds of tricyclic intermediates bearing carbamoylmethyl and aminomethyl groups at C-8. The 13,16-seco 16-nor carbamate (20a) was obtained from ent-beyeran-16-one oxime (17) by Beckmann fragmentation, hydrolysis, and Curtius rearrangement. The aza analogues inhibited recombinant ent-kaurene synthase from Arabidopsis thaliana (GST-rAtKS) with inhibition constants (IC = 1 × 10 −7 and 1 × 10 −6 50 M) similar in magnitude to the pseudo-binding constant of the bicyclic ent-copalyl diphosphate substrate (K m = 3 × 10 −7 M). Large enhancements of binding affinities (IC 50 = 4 × 10 −9 and 2 × 10 −8 M) were observed in the presence of 1 mM pyrophosphate which is consistent with a tightly bound ent-beyeranyl + /pyrophosphate − ion pair intermediate in the cyclization-rearrangement catalyzed by this diterpene synthase. The weak inhibition (IC 50 = 1 × 10 −5 M) exhibited by entbeyeran-16 exo-yl diphosphate (11), and its failure to undergo bridge rearrangement to kaurene, appear to rule out the covalent diphosphate as a free intermediate. 16-Aza-ent-beyerane is proposed as an effective mimic for the ent-beyeran-16-yl carbocation with potential applications as an active site probe for the various ent-diterpene cyclases, and as a novel, selective inhibitor of gibberellin biosynthesis in plants.

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“…When the 1 H chemical shift difference between the α-and β-Hs of the monoheteroaromatic aromatic compounds are compared, thiophene (Δδ = 0.24) is the smallest among thiophene, furan (Δδ = 1.08) and pyrrole (Δδ = 0.57). 1 The difference in 13 C chemical shifts of the α-and β-Cs also shows a similar trend: thiophene 1.5 ppm; furan 33.1 ppm, and pyrrole 10.3 ppm. 2 However, the physico-chemical properties originated by the presence of functional groups on either α-or β-position show quite different behaviors.…”

Section: Introductionmentioning

confidence: 77%

Studies on the Nuclear Magnetic Resonance Spectra of (E)-1-Aryl-3-(2- and 3-thienyl)-2-propenones and Unique Observation of⁴J and⁵J Coupling in Their¹H-¹H COSY

HanLee¹,

Jeon²,

Lee³

2011

Bulletin of the Korean Chemical Society

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1H and 13 C NMR spectra of series of (E)-1-aryl-(2-and 3-thienyl)-2-propenones, that are aldol condensation products between 2-and 3-thiophenecarbaldehydes and m-and p-substituted acetophenones, were examined to make complete assignments of the chemical shifts. Long range couplings, 4 J and 5 J, are observed in the 1 H-1 H COSY of both 2-and 3-thienyl compounds, which makes the elucidation of the conformation in solution possible. In contrast, the 2-furyl analogue shows the long range coupling phenomena, but the 3-furyl and phenyl analogues do not show similar phenomena.

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Structure Determination of Organic Compounds

Cited by 1,817 publications

References 0 publications

Oxidation of Methylthiophenes to Thiophenecarboxylic Acids

Oxidation of Methylthiophenes to Thiophenecarboxylic Acids

16-Aza-ent-beyerane and 16-Aza-ent-trachylobane: Potent Mechanism-Based Inhibitors of Recombinant ent-Kaurene Synthase from Arabidopsis thaliana

Studies on the Nuclear Magnetic Resonance Spectra of (E)-1-Aryl-3-(2- and 3-thienyl)-2-propenones and Unique Observation of⁴J and⁵J Coupling in Their¹H-¹H COSY

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Structure Determination of Organic Compounds

Cited by 1,817 publications

References 0 publications

Oxidation of Methylthiophenes to Thiophenecarboxylic Acids

Oxidation of Methylthiophenes to Thiophenecarboxylic Acids

16-Aza-ent-beyerane and 16-Aza-ent-trachylobane: Potent Mechanism-Based Inhibitors of Recombinant ent-Kaurene Synthase from Arabidopsis thaliana

Studies on the Nuclear Magnetic Resonance Spectra of (E)-1-Aryl-3-(2- and 3-thienyl)-2-propenones and Unique Observation of4J and5J Coupling in Their1H-1H COSY

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Studies on the Nuclear Magnetic Resonance Spectra of (E)-1-Aryl-3-(2- and 3-thienyl)-2-propenones and Unique Observation of⁴J and⁵J Coupling in Their¹H-¹H COSY