- Synthesis and mesomorphic characterization of some novel steroidal mesogens: A structure–property correlation
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The steroidal derivatives are found to be extremely good mesogens since their inception. Because of their inherent chirality, they have the potential to induce a wide variety of liquid crystalline phases, including frustrated phases depending upon the structure of the steroidal skeleton and the substituents attached. In this report, a series of novel monoalkoxy and dialkoxy benzoate derivatives of ergosterol and a few monoalkoxy derivatives of stigmasterol have been synthesized and their mesomorphic property has been investigated. The derivatives exhibited various mesophases including SmA, SmC*, N*, TGB and blue phases. Also, the gelation ability of some of these derivatives with various organic solvents has been examined. Furthermore, the mesomorphism of these derivatives has been compared with the analogous cholesteryl counterparts.
- Bhat S, Vanishree,Kumar, Sandeep,Raghunathan, V. A.
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- Synthesis and preliminary biological characterization of new semisynthetic derivatives of ramoplanin
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Ramoplanin is a glycolipodepsipeptide antibiotic active against Gram-positive bacteria including vancomycin-resistant enterococci. Ramoplanin inhibits bacterial cell wall biosynthesis by a mechanism different from that of glycopeptides and hence does not show cross-resistance with these antibiotics. The systemic use of ramoplanin has been so far prevented because of its low local tolerability when injected intravenously. To overcome this problem, the fatty acid side chain of ramoplanin was selectively removed and replaced with a variety of different carboxylic acids. Many of the new ramoplanin derivatives showed antimicrobial activity similar to that of the natural precursor coupled with a significantly improved local tolerability. Among them the derivative in which the 2-methylphenylacetic acid has replaced the di-unsaturated fatty acid side chain (48) was selected as the most interesting compound and submitted to further in vitro and in vivo characterization studies.
- Ciabatti, Romeo,Maffioli, Sonia I.,Panzone, Gianbattista,Canavesi, Augusto,Michelucci, Elena,Tiseni, Paolo S.,Marzorati, Ettore,Checchia, Anna,Giannone, Matteo,Jabes, Daniela,Romanò, Gabriella,Brunati, Cristina,Candiani, Gianpaolo,Castiglione, Franca
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p. 3077 - 3085
(2008/02/06)
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- The synthesis and mesomorphism of di-, tetra- and hexa-catenar liquid crystals based on 2,2′-bipyridine
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2,2′-Bipyridines are known to coordinate to a wide variety of metal centres. In this paper, liquid-crystalline two-chained (dicatenar), four-chained (tetracatenar) and six-chained (hexacatenar) bipyridines are synthesised and their mesomorphism is described. For the tetracatenar bipyridines, a full homologous series, from tetramethoxy to tetratetradecyloxy, was synthesised, and the phase diagram showed a classic progression from nematic and smectic C phases at short chain length, through a cubic phase to a columnar phase.
- Rowe, Kathryn E.,Bruce, Duncan W.
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p. 331 - 341
(2007/10/03)
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- Tailoring thermotropic cubic mesophases: Amphiphilic polyhydroxy derivatives
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Novel amphiphilic polyhydroxy compounds [N-(3,4-dialkoxybenzoyl)-1-amino-1-deoxy-D-glucitols (glucamides), N-(3,4-dialkoxybenzoyl)-1-deoxy-1-methylamino-D-glucitols, N-(3,4,5-trialkoxybenzoyl)-1-deoxy-1-methylamino-D-glucitols (N-methylgucamides), 1-benzo
- Borisch, Konstanze,Diele, Siegmar,Goering, Petra,Kresse, Horst,Tschierske, Carsten
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p. 529 - 543
(2007/10/03)
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- Influence of lateral alkoxy substitution on mesomorphic properties of copper complexes
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Coordination complexes between copper and some lateral alkoxy chain-substituted N-(4-(4'-alkoxybenzoyloxy)salicylidene)-4-n-butylaniline have been synthesized.The lateral chain was introduced on the outer ring bearing the ester function.In the case of a 3,4-disubstitution, the mesomorphic behavior is related to the number of carbons in the terminal chain.If this is too small, the mesomorphic properties of the complexes disappear.In contrast, copper complexes are liquid crystalline and show more ordered phases by comparison with the free ligand.In case of a 2,4-disubstitution, the phases are nematic and the clearing temperatures are near room temperature, but the observed phases are essentially monotropic for the ligands, as well as for the complexes.Keywords: nematic / copper complex / lateral substitution / Schiff base
- Berdague, Philippe,Perez, Felix,Courtieu, Jacques,Bayle, Jean-Pierre
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p. 335 - 343
(2007/10/02)
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