1,721,089 research outputs found
N-haloamidines. VII. 4-amino-5-chloroimidazoles and 4-amino-5-unsubstituted imidazoles from N-chloro-N′-arylbenzamidines and 1,1-diaminoethenes
No full textN-chloro-N′-arylbenzamidines react with 1,1-diaminoethenes to give in good yields 4-amino-5-chloroimidazoles. The behaviour of these compounds in some nucleophilic substitution reactions and their reduction to 4-amino-5-unsubstituted imidazoles is reported
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
Iminophosphoranes in heterocyclic chemistry. A simple one-pot synthesis of dihydropyrimidines and pyrimidines
No full textThe condensation of N-triphenylphosphoraniliden-benzamidine with acyclic α,β-unsaturated aldehydes produces dihydropyrimidines in good to high yields. The methodology has been extended to alicyclic and heterocyclic aldehydes
Carotenoids in bird plumage: the complement of red pigments in the plumage of wild and captive bullfinch (Pyrrhula pyrrhula)
No full textWe have studied the carotenoid pigments in the red plumage of male bullfinch (Pyrrhula pyrrhula) immediately following capture and after the completion of the moult in captivity under dietary control. Astaxanthin, adonirubin, and α-doradexanthin, as well as papilioeritrinone and canthaxanthin (in lower amounts) are in every case the dominant carotenoids in the plumage pigment of wild individuals. α-Doradexanthin is responsible for the reddish-rose colour, which captive individuals adopt after a diet consisting mainly of lutein as disposable carotenoid. The red pigmentation biogenesis of captive bullfinch is compared with those of other red pigmented Carduelinae in which male individuals usually lose the red colour in captivity, namely Carpodacus roseus, Carpodacus rubricilloides, Uragus sibiricus, Carduelis cannabina, Carduelis flammea, Loxia curvirostra and Pinicola enucleator
The chemical structure of the pigments in Ara macao plumage,
No full textParrots (Psittaciformes) harbor unusually bright, non-carotenoid, feather pigments. We successfully extracted and purified a sufficient quantity of pigment from the red plumage of the Scarlet Macaw (Ara macao) for a partial chemical analysis. The extracts were analyzed by HPLC coupled with UV-VIS and mass spectroscopy before and after total hydrogenation. We found at least four pigment components. We propose a linear polyenal structure comparable with the molecules tetradecahexenal, hexadecaheptenal, octadecaoctenal and eicosanonenal
Polyunsaturated linear aldehydes and their derivatives with antiradical and anti-tumoral activity
No full textThe invention relates to polyunsaturated linear aldehydes and derivatives thereof which can be extracted from the feathers or tissues of parrots of prepared synthetically with antioxidant, antitumoral and anti-inflammatory activity, and which are useful in the prevention and treatment of cardiovascular, inflammatory, atherosclerotic, proliferative cell and tumour damage and the prevention of alterations caused by ageing
Substituted 1 Benzyl-4-(benzylidenimino)-4-phenylazetidin-2-ones : synthesis, thermal and photochemical reactions
No full textThe title compounds were synthesised from 1,3-diazabuta-1,3-dienes and ketenes. Thermal and photochemical ring expansion reactions to 5,6-dihydro-3H-pyrimidin-4-ones are also described
Synthetic response modifiers. Part II. Synthesis and immunomodulatory properties of some N2[w-(pyrimidin-1-yl)-carboxyalkyl]-L-arginines
No full textSynthesis of new cytosine and thymine derivatives of potential immunomodulatory activity
No full textThe synthesis and the main chemical and physical properties of some N1 alkylated cytosines and thymines are described
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