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Susanta Kumar Manna Arabinda Mandal Suresh Kumar Mondal Jayanta K. Ray Mahiuddin Baidya 《合成通讯》2013,43(5):625-634
A novel synthesis of 3,4-fused furans (both tricyclic and bicyclic) through platinum-catalyzed cyclization of 3-(2-formylcycloalkenyl)-acrylic amides 2 in methanol is described (up to 90% yield). Tricyclic 3,4-fused dihydrofuran derivatives were also obtained via reductive cyclization of 2. The substrates 2 were obtained from β- bromovinyl aldehydes by a Pd-catalyzed Heck reaction. 相似文献
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An oxidative trifunctionalization of aryl alkynoates has been devised via the chalcogenide radical triggered intramolecular 1,4‐aryl migration/decarboxylation cascade to prepare 1,1‐dichalcogenide tetrasubstituted alkenes in high yields (up to 98 %). This operationally simple reaction proceeds under metal‐free conditions, can be executed on gram scale, and highlights formal 1,1‐difunctionalization of alkynes. Synthetic potential of this protocol was demonstrated through a twofold cascade rearrangement to access highly conjugated tetra‐selenylated alkenes along with a cross‐dehydrogenative annulation to prepare fluorene derivative. 相似文献
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Significant Structural Differences between Transient Amyloid‐β Oligomers and Less‐Toxic Fibrils in Regions Known To Harbor Familial Alzheimer′s Mutations 下载免费PDF全文
Bidyut Sarkar Dr. Venus Singh Mithu Bappaditya Chandra Arghya Mandal Muralidharan Chandrakesan Debanjan Bhowmik Prof. Perunthiruthy K. Madhu Prof. Sudipta Maiti 《Angewandte Chemie (International ed. in English)》2014,53(27):6888-6892
Small oligomers of the amyloid β (Aβ) peptide, rather than the monomers or the fibrils, are suspected to initiate Alzheimer′s disease (AD). However, their low concentration and transient nature under physiological conditions have made structural investigations difficult. A method for addressing such problems has been developed by combining rapid fluorescence techniques with slower two‐dimensional solid‐state NMR methods. The smallest Aβ40 oligomers that demonstrate a potential sign of toxicity, namely, an enhanced affinity for cell membranes, were thus probed. The two hydrophobic regions (residues 10–21 and 30–40) have already attained the conformation that is observed in the fibrils. However, the turn region (residues 22–29) and the N‐terminal tail (residues 1–9) are strikingly different. Notably, ten of eleven known Aβ mutants that are linked to familial AD map to these two regions. Our results provide potential structural cues for AD therapeutics and also suggest a general method for determining transient protein structures. 相似文献