7-Azetidinylquinolones as Antibacterial Agents. 2. Synthesis and Biological Activity of 7-(2,3-Disubstituted-1-azetidinyl)-4-oxoquinoline- and -1,8-naphthyridine-3-carboxylic Acids. Properties and Structure-Activity Relationships of Quinolones with an Azetidine Moiety

Abstract

A series of 7-(2,3-disubstituted-1-azetidinyl)-1,4-dihydro-6-fluoro-4- oxoquinoline- and -1,8-naphthyridine-3-carboxylic acids, with varied substituents at the 1-, 5-, and 8-positions, was prepared to study the effects on potency and physicochemical properties of the substituent at position 2 of the azetidine moiety. The activity of the title compounds was determined in vitro against Gram-positive and Gram-negative bacteria, and the in vivo efficacy of selected derivatives was determined using a mouse infection model. The X-ray crystal structures of 6b, 6c, and 6d were found to be in reasonable agreement with the corresponding AM1 calculated geometries. Correlations between antibacterial potency of all the synthesized 7-azetidinylquinolones and naphthyridines and their calculated electronic properties and experimental capacity factors were established. Antibacterial efficacy and pharmacokinetic and physicochemical properties of selected derivatives were compared to the relevant 7-(3-amino-1-azetidinyl) and 7-(3-amino-3-methyl-1-azetidinyl) analogues (for Part 1, see: J. Med. Chem. 1993, 36, 801-810). A combination of a cyclopropyl or a substituted phenyl group at N-1 and a trans-3-amino-2-methyl-1-azetidinyl group at C-7 conferred the best overall antibacterial, pharmacokinetic, and physicochemical properties to the azetidinylquinolones studied.

Synthesis of New Quinolone Antibiotics Utilizing Azetidine Derivatives Obtained from 1-Azabicyclo[1.1.0]butane

“…Since the desirable reaction did not proceed under the same conditions as described in Table 3, we focused on N-benzyl-3-bromoazetidine (13) 8) which can be exploited to synthesize various azetidine derivatives via suitable nucleophilic substitution reaction. The compound 13 was obtained via two steps of reactions involving the ringopening reaction of ABB (3) with HBr to give 3-bromoazetidine hydrobromide (12) followed by benzyl protection of the N1 group, but this reaction procedure resulted in a low yield (24% total yield).…”

“…13 C-NMR spectra were recorded on a JEOL JNM-AL300 (75 MHz) or JEOL JNM-AL400 (100 MHz) spectrometer with complete proton decoupling. Chemical shifts are given in d values (ppm) using tetramethylsilane (TMS) as an internal standard.…”

“…Although several examples of 7-azetidinylquinolones have been reported, [12][13][14][15] there have been not many prominent quinolone antibiotics bearing the azetidinyl substituent groups thus far. We envisaged that the introduction of azetidine derivatives onto the C7 position of the quinolone nucleus might enhance their antibacterial activities against MRSA.…”

“…These azetidine moieties have often been found in many natural products 11) and biologically active compounds such as carbapenems 1) and new quinolone antibiotics. [12][13][14][15] 1,3,3-Trinitroazetidine (TNAZ), 16,17) an insensitive high explosive, was also synthesized by using ABB (3). In recent years, we established an efficient method for synthesis of ABB (3) starting from allylamine (1) via 2,3-dibromopropylamine hydrobromide (2), and reported its application to the synthesis of several azetidine derivatives, as shown in Chart 1.…”

“…10) We now describe, in detail, a convenient method of synthesizing several 3-sulfenyl-and 3-aminoazetidine derivatives utilizing ABB (3), and we discuss the synthesis and antibacterial activities of new quinolone antibiotics incorporating these azetidine derivatives to the C7 position. Although several examples of 7-azetidinylquinolones have been reported, [12][13][14][15] there have been not many prominent quinolone antibiotics bearing the azetidinyl substituent groups thus far. We envisaged that the introduction of azetidine derivatives onto the C7 position of the quinolone nucleus might enhance their antibacterial activities against MRSA.…”