180293-27-0Relevant academic research and scientific papers
Neighboring Component Effect in a Tri-stable [2]Rotaxane
Wang, Yuping,Cheng, Tao,Sun, Junling,Liu, Zhichang,Frasconi, Marco,Goddard, William A.,Fraser Stoddart
, p. 13827 - 13834 (2018)
The redox properties of cyclobis(paraquat-p-phenylene)cyclophane (CBPQT4+) render it a uniquely variable source of recognition in the context of mechanically interlocked molecules, through aromatic donor-acceptor interactions in its fully oxidized state (CPBQT4+) and radical-pairing interactions in its partially reduced state (CBPQT2(a€￠+)). Although it is expected that the fully reduced neutral state (CBPQT(0)) might behave as a ?€-donating recognition unit, resulting in a dramatic change in its binding properties when compared with the other two redox states, its role in rotaxanes has not yet been investigated. To address this challenge, we report herein the synthesis of a tri-stable [2]rotaxane in which a CBPQT4+ ring is mechanically interlocked with a dumbbell component containing five recognition sites - (i) a bipyridinium radical cation (BIPY(a€￠+)) located centrally along the axis of the dumbbell, straddled by (ii) two tetrafluorophenylene units linked to (iii) two triazole rings. In addition to the selective recognition between (iv) the CBPQT4+ ring and the triazole units, and (v) the CBPQT2(a€￠+) ring and the reduced BIPY(a€￠+) unit in the dumbbell component, investigations in solution have now confirmed the presence of additional non-covalent bonding interactions between the CBPQT(0) ring, acting as a donor in its neutral state, and the two tetrafluorophenylene acceptors in the dumbbell component. The unveiling of this piece of molecular recognition in a [2]rotaxane is reminiscent of the existence in much simpler, covalently linked, organic molecules of neighboring group participation (anchimeric assistance giving way to transannular interactions) in small-, medium-, and large-membered rings.
Synthesis and pharmacological evaluation of fluorescent and photoactivatable analogues of antiplasmodial naphthylisoquinolines
Bringmann, Gerhard,Gampe, Christian M.,Reichert, Yanina,Bruhn, Torsten,Faber, Johan H.,Mikyna, Martin,Reichert, Matthias,Leippe, Matthias,Brun, Reto,Gelhaus, Christoph
, p. 6104 - 6115 (2008/09/16)
The naphthylisoquinoline (NIQ) alkaloids from tropical Ancistrocladaceae and Dioncophyllaceae plants show high antiplasmodial activities in vitro and in vivo, even against chloroquine-resistant strains of the malaria pathogen. For the directed optimization of these activities, an investigation of the mode of action seems most rewarding. We have therefore embarked on the identification of the respective target protein in Plasmodium falciparum. For this purpose, we have developed a flexible pathway for the synthesis of a chemically divergent series of photoactive and fluorescent derivatives of such alkaloids and succeeded in preparing the first functionalized NIQ derivatives, 10, 12, and 35, suited for fluorescence and photoaffinity labeling experiments. Pharmacological investigations ensured that the modified alkaloid derivatives retained their antiplasmodial activity. The work may pave the way for a further improvement of the activity of these natural products and will thus increase their pharmacological potential as a valuable lead structure against the widespread tropical disease malaria.
Ginkgolide derivatives for photolabeling studies: Preparation and pharmacological evaluation
Str?mgaard, Kristian,Saito, D. Roland,Shindou, Hideo,Ishii, Satoshi,Shimizu, Takao,Nakanishi, Koji
, p. 4038 - 4046 (2007/10/03)
The terpene trilactones (TTLs), ginkgolides and bilobalide, are structurally unique constituents of Ginkgo biloba extracts, which exhibit various neuromodulatory properties. Although the TTLs are believed to be responsible for some of these effects, the s
Synthesis of phytyl- and chroman-derivatized photoaffinity labels based on α-tocopherol
Lei, Huangshu,Atkinson, Jeffrey
, p. 2560 - 2567 (2007/10/03)
Photoaffinity analogues of α-tocopherol have been prepared by substituting photosensitive functional groups at either the terminus of an alkyl chain of varying length mimicking the phytyl tail or on C-3 of the chroman portion of tocopherol. The alkyl chain-modified compounds 2a-d contain a hexyl to nonyl alkyl chain extending from C-2 of the chroman, terminating in a tetrafluoroazidobenzyloxy group. These compounds were prepared starting from the commercially available Trolox acid 4, followed by esterification, protection, and reduction to the silyl-protected Trolox aldehyde 7, which was coupled using Wittig chemistry to different ω- hydroxyphosphonium bromides. Reduction of the alkene product, coupling with p-azidotetrafluorobenzyl bromide, and deprotection of the phenolic silyl group gave compounds 2a-d in excellent yields. Chroman-functionalized photoaffinity labels were synthesized starting from the protected tocopherol chromene 16b which was a key intermediate for preparation of a 3-hydroxy derivative, either by reduction of epoxides produced directly with Jacobsen's catalysts or by treatment with NBS in wet DME to give two stereoisomeric bromohydrins which were cyclized and reduced to give the phenol-protected C-3 alcohols 19a,b. These alcohols were then converted to diazoacetate esters, and the protecting group was removed to give 3-diazoacetoxy α-tocopherols 3a,b.
Synthesis of photoaffinity label analogues of α-tocopherol
Lei, Huangshu,Marks, Virginia,Pasquale, Tony,Atkinson, Jeffrey K.
, p. 3453 - 3458 (2007/10/03)
Photoaffinity analogues of α-tocopherol have been synthesized that incorporate the photosensitive 4-azido-2,3,5,6-tetrafluorobenzyloxy group at the terminus of unbranched analogues of the naturally occurring phytyl side chain. An intermediate from these s
The photochemistry of various para-substituted tetrafluorophenyl azides in acidic media and the formation of nitrenium ions
Michalak, Jacek,Zhai, Hong Bin,Platz, Matthew S.
, p. 14028 - 14036 (2007/10/03)
Laser flash photolysis of polyfluorinated aryl azides in acetonitrile at ambient temperature produces singlet nitrenes which have lifetimes of tens to hundreds of nanoseconds. The lifetimes are controlled by ring expansion and intersystem crossing to the
