THE CHEMISTRY OF VITAMIN E. VII. PREPARATION OF QUINONES FROM METHYLPHENOLS<sup>1</sup>

Smith, Lee Irvin; Opie, J. W.; Wawzonek, S.; Prichard, W. W.

doi:10.1021/jo01215a015

Cited by 28 publications

(22 citation statements)

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“…The missing unit could be either a 3,4-disubstituted pyrazole or a 2,4-disubstituted imidazole ring, but the latter fits better a biosynthetic pathway based on condensation of two tryptamine precursors. This postulate was confirmed by NMR data for C-4 and H-4 in 1 ( 13118.0,18 7.96, «/C_H = 201 Hz), 12 and by 13C-1H…”

supporting

confidence: 55%

“…1 H and 1SC NMR Data for Topsentins: Chemical Shift, ppm, from Me2SO (Multiplicity; «7, Hz)" > assign.. 3 Syntheses of Neotopsentin and Related Compounds. To investigate further the structure-activity relationship, we prepared the 5"-analogue of topsentin, which we have named neotopsentin (7), from 5"-(benzyloxy) indole via the isolated glyoxalylindole 21. This preparation yielded a mixture of the O-benzyl products 22-24 as well as deoxytopsentin (6) in yields of 11, 9, 3, and 28%, respectively.…”

mentioning

confidence: 99%

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Topsentin, bromotopsentin, and dihydrodeoxybromotopsentin: antiviral and antitumor bis(indolyl)imidazoles from Caribbean deep-sea sponges of the family Halichondriidae. Structural and synthetic studies

Tsujii¹,

Rinehart²,

Gunasekera³

et al. 1988

J. Org. Chem.

150

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supporting

confidence: 55%

mentioning

confidence: 99%

Topsentin, bromotopsentin, and dihydrodeoxybromotopsentin: antiviral and antitumor bis(indolyl)imidazoles from Caribbean deep-sea sponges of the family Halichondriidae. Structural and synthetic studies

Tsujii¹,

Rinehart²,

Gunasekera³

et al. 1988

J. Org. Chem.

150

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“…All-rac-α-tocopheryl acetate (≥95%), farnesol (≥95%), and R,S-Trolox (1a, 97%) were purchased from Sigma-Aldrich Co. (Steinheim, Germany). The syntheses of compounds 1b [22], 1c [23], 4, 5, and 10 [21] were carried out according to the literature. Synthesis of phosphonium salt 9 is described in the Supplementary File S1.…”

Section: General Informationmentioning

confidence: 99%

Synthesis, DFT Calculations, and In Vitro Antioxidant Study on Novel Carba-Analogs of Vitamin E

et al. 2019

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Vitamin E is the most active natural lipophilic antioxidant with a broad spectrum of biological activity. α-Tocopherol (α-T), the main representative of the vitamin E family, is a strong inhibitor of lipid peroxidation as a chain-breaking antioxidant. Antioxidant and antiradical properties of vitamin E result from the presence of a phenolic hydroxyl group at the C-6 position. Due to stereoelectronic effects in the dihydropyranyl ring, the dissociation enthalpy for phenolic O–H bond (BDEOH) is reduced. The high chain-breaking reactivity of α-T is mainly attributed to orbital overlapping of the 2p-type lone pair on the oxygen atom (O1) in para position to the phenolic group, and the aromatic π-electron system. The influence of the O1 atom on the antioxidant activity of vitamin E was estimated quantitatively. The all-rac-1-carba-α-tocopherol was synthesized for the first time. Along with model compounds, 1-carba-analog of Trolox and its methyl ester were screened for their in vitro antioxidant activity by inhibition of styrene oxidation, and for the radical-reducing properties by means of 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH) scavenging assay. To study the antioxidant activity, density functional theory (DFT) was also applied. Reaction enthalpies related to HAT (hydrogen atom transfer), SET–PT (sequential electron transfer—proton transfer), and SPLET (sequential proton loss—electron transfer) mechanisms were calculated.

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“…i.HV. sublimiert oder nach den in der Literatur angegebenen Verfahren synthetisiert (2,3-Dimethyl-1,4-benzochinon (15c) [32], 2,6-Dimethoxy-1,4-benzochinon (150 [33], 2,3,5-Tnmethyl-l,Cbenzochinon (15d) [34], 2,3-Dimethyl-1,4-naphthochinon (5 c) [35]). …”

Section: Experimenteller Teilunclassified

Spirocyclische 3‐Oxazoline durch 1,3‐dipolare Cycloaddition von Benzonitrilio‐2‐propanid mit 1,4‐Chinonen

Stegmann

Uebelhart

Heimgartner

1983

Helvetica Chimica Acta

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On irradiation with light of wavelength 290-350 nm, 2,2-dimethyl-3-phenyl-2 H-azirine (lb) reacts with 1,4-naphthoquinone to give the 1H-benzo Iflisoindol-4,9-dione (11) (Scheme 3) via cycloaddition of the benzonitrilio-2-propanide (2 b) onto the quinone C, C-double bond. With 2-methyl-and 2,3-dimethyI-l, 4-naphthoquinone, the nitrile ylide 2 b undergoes cycloaddition preferentially onto the C, 0-double bond of the quinone, leading to spiro-oxazolines 12 and 14 (Scheme 4 ) . Steric as well as electronic effects can be discussed to explain the observed site selectivity of the cycloaddition.With the 1,4-benzoquinones 15a, 15b, 15d and 15f, nitrile ylide 2b undergoes the 1,3-dipoIar cycloaddition exclusively onto the C, 0-double bond. The corresponding spiro-oxazolines have been isolated in 17-32% yield. This contrasts with the previously reported results with benzonitrilio-phenylmethanide (2 a), which undergoes cycloaddition to the C, C-double bond of 1,4-benzoquinones (cf. [ 11). This difference in the site selectivity of the 1,3-dipolar cycloaddition can be explained with Houk's concept of LUMO-polarization, that is, the stronger nucleophilic dipol2 b polarizes the LUMO of a a,P-unsaturated carbonyl compound more efficient than the less nucleophilic 2 a.This leads to a preference of the cycloaddition to the C,O-double bond in the case of 2b.With 2,3-dimethyI-(15c) and 2,3,5,6-tetramethyl-l, 4-benzoquinone (15e), nitrile ylide 2 b undergoes C, 0as well as C, C-cycloaddition (Schemes 7 and 8 ) .1. Einleitung. -Vor einiger Zeit haben wir uber photochemisch induzierte Cycloadditionen von 2,3-Diphenyl-2H-azirin (la) mit 1,4-Chinonen berichtet [ 11. Bei dieser Reaktion werden durch 1,3-dipolare Cycloadditionen des bei der Photolyse von l a ') *) Vorgetragen von H. H. an der Euchem-

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THE CHEMISTRY OF VITAMIN E. VII. PREPARATION OF QUINONES FROM METHYLPHENOLS¹

Cited by 28 publications

References 0 publications

Topsentin, bromotopsentin, and dihydrodeoxybromotopsentin: antiviral and antitumor bis(indolyl)imidazoles from Caribbean deep-sea sponges of the family Halichondriidae. Structural and synthetic studies

Topsentin, bromotopsentin, and dihydrodeoxybromotopsentin: antiviral and antitumor bis(indolyl)imidazoles from Caribbean deep-sea sponges of the family Halichondriidae. Structural and synthetic studies

Synthesis, DFT Calculations, and In Vitro Antioxidant Study on Novel Carba-Analogs of Vitamin E

Spirocyclische 3‐Oxazoline durch 1,3‐dipolare Cycloaddition von Benzonitrilio‐2‐propanid mit 1,4‐Chinonen

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THE CHEMISTRY OF VITAMIN E. VII. PREPARATION OF QUINONES FROM METHYLPHENOLS1

Cited by 28 publications

References 0 publications

Topsentin, bromotopsentin, and dihydrodeoxybromotopsentin: antiviral and antitumor bis(indolyl)imidazoles from Caribbean deep-sea sponges of the family Halichondriidae. Structural and synthetic studies

Topsentin, bromotopsentin, and dihydrodeoxybromotopsentin: antiviral and antitumor bis(indolyl)imidazoles from Caribbean deep-sea sponges of the family Halichondriidae. Structural and synthetic studies

Synthesis, DFT Calculations, and In Vitro Antioxidant Study on Novel Carba-Analogs of Vitamin E

Spirocyclische 3‐Oxazoline durch 1,3‐dipolare Cycloaddition von Benzonitrilio‐2‐propanid mit 1,4‐Chinonen

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THE CHEMISTRY OF VITAMIN E. VII. PREPARATION OF QUINONES FROM METHYLPHENOLS¹