New inhibitors of colony spreading in Bacillus subtilis and Bacillus anthracis
摘要:
We have recently characterized sliding motility in Bacillus subtilis strains that lack functional flagella, and here describe the discovery of inhibitors of colony spreading in these strains as well as the aflagellate pathogen, Bacillus anthracis. Aflagellate B. subtilis strains were used to screen for new types of antibacterials that might inhibit colony spreading on semi-solid media. From a diverse set of organic structures, p-nitrophenylglycerol (NPG), an agent used primarily in clinical laboratories to control Proteus swarming, was found to inhibit colony spreading. The four stereoisomers of NPG were synthesized and tested, and only the 1R,2S-(1R-anti) and 1R,2R-(1R-syn) NPG isomers had significant activity in a quantitative colony spreading assay. Twenty-six NPG analogs and related structures were synthesized and tested to identify more active inhibitors. p-Methylsulfonylphenylglycerol (p-SPG), but not its ortho or meta analogs, was found to be the most effective of these compounds, and synthesis and testing of all four p-SPG stereoisomers showed that the 1R-anti-isomer was the most active with an average IC50 of 16 mu M (3-5 mu g mL (1)). For B. anthracis, the colony-spreading IC50 values for 1R-anti-SPG and 1R-anti-NPG are 12 mu M (2-4 mu g mL (1)) and >150 mu M, respectively. For both Bacillus species tested, 1R-anti-SPG inhibits colony spreading of surface cultures on agar plates, but is not bacteriostatic or bacteriocidal in liquid cultures. Work is in progress to find the cellular target(s) of the NPG/SPG class of compounds, since this could lead to an understanding of the mechanism(s) of colony spreading as well as design and development of more potent inhibitors for the control of B. anthracis surface cultures. (C) 2011 Elsevier Ltd. All rights reserved.
Backbone-homologated amino acids have been synthesized, containing three vicinal fluorine atoms placed stereospecifically along the carbon chain. Different trifluoro stereoisomers are found to have contrasting conformations, consistent with known stereoelectronic effects associated with C–F bonds.
Kinetic resolution of allylic alcohols via stereoselective acylation catalyzed by lipase PS-30
作者:Peiran Chen、Peng Xiang
DOI:10.1016/j.tetlet.2011.08.093
日期:2011.11
By using lipase PS-30 as catalyst, the kineticresolution of a series of racemic allylic alcohols has been achieved via stereoselective acylation. The value of kinetic enantiomeric ratio (E) reached up to 968. Substituent effect is briefly discussed.
A short stereoselective synthesis of (−)-chloramphenicol and (+)-thiamphenicol
作者:G. Bhaskar、V. Satish Kumar、B. Venkateswara Rao
DOI:10.1016/j.tetasy.2004.03.007
日期:2004.4
A common strategy for the synthesis of (-)-chloramphenicol and (+)-thiamphenicol is described. These antibiotics have been synthesized from commercially available 4-nitrobenzaldehyde and 4-(methylthio)benzaldehyde in three and four steps, respectively. (C) 2004 Elsevier Ltd. All rights reserved.