1,721,012 research outputs found
Isomerization of 4-Aminobenzofurans to 4-Hydroxyindoles.
No full text4-Amino-2-methylbenzofurans are quantitatively converted to 4-hydroxy-2-methylindoles in acidic medium. The rearrangement mechanism involves the ring opening of the furan ring to produce an intermediate carbocation, which undergoes ring closure to the indole system. Isomerization takes place only in the presence of a methyl substituent in 2 position
13C-NMR Spectra and carbon-proton coupling constants of various annulated furocoumarins
No full textThe 13C NMR spectra of variously annulated methylfurocoumarins are reported. The assignments of chemical shifts for all the C resonances have been achieved by using carbon-proton coupling costants, relaxation efficiency considerations and shift effects caused by the introduction of methyl groups at various position of the furocoumarin nucleus. Substituent effects on chemical shifts and C-H coupling constants are discussed
Synthesis of azapsoralen derivatives.
No full textA number of new isosters of psoralen, in wich the benzene ring of psoralen is substituted with a pyridine one were synthesized. The synthesis were performed starting from the appropriate hydroxypyranopyridinone on which the furan ring was built. Several derivatives in which an additional cyclohexene or benzene ring is condensed to the furan ring moiety have also been prepared
1H-NMR Spectra of variously annulated furocoumarins
No full textThe 1H NMR spectra of variously annulated methylfurocoumarins are reported. The assignment of chemical shifts for all the protons was achieved by using carbon-proton coupling costants, and shift effects induced by the introduction of methyl groups at various positions on the furocoumarin nucleus
Synthesis of some methylfurochromones as potential photochemotherapeutic agents.
No full textA number of new methylfurochromones with a linear psoralen-loke structure or an angular angelicin-like one were synthesized. The synthesis were performed starting from the appropriate 7-hydroxychromones on which the fura ring was built. Methyl groups were introduced into positions which look most promising for enhancement of the photoreactivity of the compound toward DNA
New synthesis of pyrrolo[3,2,1-ij]quinolin-4-one derivatives.
No full textA new convenient synthesis of pyrrolo[3,2,1-ij]quinolin-4-one derivatives is described. In this method, methyl-7-hydroxquinoline-2-ones are the starting materials onto which the third pyrrolo ring is condensed directly, yielding dehydrogenated methyl-9-hydroxypyrrolo[3,2,1-ij]quinolin-4-ones
Pyrrolocoumarin derivatives as potential photoreagents toward DNA.
No full textA number of new methyl derivatives of linear and angular pyrrolocoumarins were synthesized by direct Fischer’s indole synthesis. In the same way some linear and angular pyranocarbazolones. The synthesis were performed starting from the appropriate methyl-7-aminocoumarins and methyl groups were introduced into positions which look most promising for the photoreactivity toward DNA
3,4 AND 4',5'-PHOTOCYCLOADDUCTS BETWEEN 4'-METHYLANGELICIN AND THYMINE FROM DNA
No full textTwo C4-cycloadducts between 4′-methylangelicin and thymine were isolated from the photo-reaction (365 nm) between this furocoumarin and DNA. Their capacity to undergo photoreversion at 254 nm and their spectroscopic and NMR data allowed us to assign furan- and pyrone-side structures, respectively, to these photocompounds. The former adduct has a cis-syn configuration; the latter. which was also isolated from a photoreaction between the furocoumarin and thymine in water-methanol solution, was assigned a cis-anti structure
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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