- Studies on Anti-MRSA parenteral cephalosporins I. Synthesis and antibacterial activity of 7
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In order to improve the antibacterial activity of cefozopran (CZOP) against methicillin-resistant Staphylococcus aureus (MRSA), we initiated chemical modification to introduce a 2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-hydroxyimino acetyl group at the C-7 position and a 3- or 6-substituted imidazo[1,2-b]pyridazinium or 5-substituted imidazo[1,2-a]pyridinium group at the C-3' position. Although this approach successfully enhanced the anti-MRSA activity of CZOP two to eight times, a slight decrease in the activity against Gram-negative bacteria including Pseudomonas aeruginosa was involved. Among the novel derivatives, 3-(6-aminoimidazo [1,2-b]pyridazinium-1-yl) methyl-7β-[2-(5-amino -1,2,4-thiadiazol-3-yl) -2(Z)-hydroxyiminoacetamidol]-3-cephem-4-carboxylate (44a) showed an excellent balance of activity against MRSA and Gram-negative bacteria.
- Ishikawa,Iizawa,Okonogi,Miyake
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p. 1053 - 1070
(2007/10/03)
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- Synthesis of HR 916 K: An efficient route to the pure diastereomers of the 1-(pivaloyloxy)ethyl esters of cephalosporins
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HR 916 K (5), the 1-(S)-(pivaloyloxy)ethyl prodrug ester of the cephalosporin cefdaloxime, exhibits a significantly higher oral bioavailability than the 1-(R) diastereomer HR 916 J. An efficient synthesis of HR 916 K was developed. The separation of the diastereomers was achieved by precipitation of the 1-(R)-hydrochloride 9 followed by crystallization of the 1-(S)-amine 10 (de > 96%). The 1-(R) diastereomer 9 was recycled by acidic saponification or enzymatic cleavage to AMCA (7). The amine 10 was acylated with mercaptobenzothiazole thioesters or mixed anhydrides, prepared from carboxylic acids 13 and 14, in almost quantitative yield. Deprotection of the oxime and formation of the tosylate proceeded in one step. Using thioester 18, we obtained HR 916 K (5) from AMCA (7) in 42% yield. VCH Verlagsgesellschaft mbH, 1996.
- Defossa, Elisabeth,Fischer, Gerd,Gerlach, Uwe,Hoerlein, Rolf,Isert, Dieter,Krass, Norbert,Lattrell, Rudolf,Stache, Ulrich,Wollmann, Theo
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p. 1743 - 1749
(2007/10/03)
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- Process for the preparation of cephem prodrug esters
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The invention relates to a process for the preparation of cephem prodrug esters of the formula: STR1 in which R1 is C1 -C5 -alkanoyloxy-C1 -C3 -alkyl or C1 -C5 -alkoxycarbonyloxy
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