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111.
C. Sadasivan Vasantha Pattabhi N. Gautham Saradha Vasanth 《Journal of chemical crystallography》1993,23(4):339-344
Vicolide A to D, sesquiterpenoid lactones, were isolated from Vicoa indica and crystal structure of A and D were established by X-ray analysis. The structures were solved by direct methods and refined to an R index of 0.09. Vicolide B and D are reported to have anti-fertility activity while A and C are devoid of this activity. Conformational features of B and C are similar but differ from those of A and C.DCB Contribution No. 805. 相似文献
112.
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114.
Considering the importance ofE
6 as the grand unification group in superstring theories, several breakdown patterns ofE
6 through maximal subgroups are studied. The Higgs which break the low energy group and give masses to the fermions are determined
in each case. At each scale we consider minimal Higgs and apply extended survival hypothesis to determine the limits on the
mass scales. The combination of intermediate mass scales that give rise to acceptable electroweak mixing angle and unification
mass is determined. Proton decay rate is found to be acceptable in all cases except one. 相似文献
115.
116.
Vasantha Pattabhi 《Pramana》1976,6(5):299-304
Semi-empirical calculations have been done on hexaphenyl benzene, triphenyl benzene ands-triphenyl triazine free molecules and the results are compared with X-ray crystal structure studies. The conformation of
isolated molecule differs from that found in crystals. The agreement improves when packing forces are also included in the
minimum energy calculations.
Contribution No. 419, from the Department of Crystallography and Biophysics, University of Madras, Guindy, Madras 600025. 相似文献
117.
A series a novel of 1,2-disubstituted benzimidazole-5-carboxylates were prepared by the one-pot nitroreductive cyclization route using sodium dithionite, and its effect on N-debenzylation has been described. Different ethyl 4-(alkyl/arylamino)-3-nitrobenzoates were reacted with various aromatic/heteroaromatic aldehydes in dimethyl sulfoxide to yield the target benzimidazoles in good yield and purity. Wide varieties of aldehydes used for the cyclization were found to be susceptible under the reaction conditions. This method afforded the products within a very short reaction time and isolation was an easy workup procedure. Debenzylation resulting in the cleavage of the N-benzyl group was observed under experimental conditions with sodium dithionite without the aid of any cocatalyst and the presence of ethanol increased the extent of debenzylation. 相似文献