Musa Z. Nazer

Thienopyridinone antibacterials : Synthesis and antibacterial activity of some 7-aryl-2-chloro-4,7-dihydro-4-oxothieno[2,3-b]pyridine-5-carboxylic acids

Abstract A series of 7-aryl-4-oxothieno[2,3- b ]pyridine-5-carboxylic acids 8 and their methyl esters 7 were synthesized by intramolecular cyclization of the respective 3- N -arylamino-2-(2,5-dichloro-3-thenoyl) acrylates 6 . The latter are accessible from methyl 3-ethoxy-2-(2,5-dichloro-3-thenoyl) acrylate 5 which, in turn, is obtained via the parent β-keto ester 4 . Of the present series, the 7-( p -hydroxyphenyl) and 7-(2′,4′-difluorophenyl) derivatives 8e,i possess the highest activity especially against Klebsiella pneumoniae, Escherichia coli and Staphylacoccus aureus (MICs of 8e/8i ∩ 0.06:0.25, 0.5:1.0 and 1.0:2.0 μg/mL, respectively).

Oxides of 3-methyl-1,2,4-benzotriazine

Abstract The previously prepared 3-methyl-1,2,4-benzotriazine oxide 1 is shown to be the 4-oxide 5 . Synthesis and structures of other isomeric and related oxides are described. A modification of a previously described synthesis of 1,2,4-benzotriazines produces purer products in higher yields.

Circular dichroism—LVII : Chiroptical properties of some α-halo- propionanilides

Abstract The CD of the anilides of α-halo-propionic acids depends on solvent and substitution of the aromatic ring. Changes of the CD with solvent can be explained by taking into account three conformers (G, A + and A − of Fig 1). The CD band around 250 nm is negative for derivatives of the l -acids in all solvents except hydrocarbons in which it is positive. The 1 L b band Cotton effects are very weak or not observed. The 1 L a —CD band is much stronger in the m - and o- substituted anilides than in-the p - or unsubstituted anilides.

Synthesis of chiroptical properties of some N-(3-methyl-2-quinoxaloyl) l-amino acids and their dioxides

A number of N-(3-methyl-2-quinoxaloyl) l-α-amino acids and esters, and their 1,4-dioxides have been prepared. The quinoxaline derivatives of aliphatic and aromatic l-α-amino acids exhibits enantiomorphic CD spectra in ethanol as well as in ethanolic KOH. However, the corresponding quinoxaline-1,4-dioxide derivatives of the l-α-aliphatic and l-α-aromatic amino acids show, in organic solvents, similar CD spectra. This behaviour is attributed to differences in conformational equilibria in both the quinoxaline and the quinoxaline-1,4-dioxide series NMR and mass spectra of these compounds are discussed.

Ring Transformation of Heterocycles: Part 3. A Conversion of 4-Amino-D2-1,2,4-oxadiazolines into 2-Arylamino-1,3,4-thiadiazoles and Oxaanalogues

4-Amino-Δ 2 -1,2,4-oxadiazolines (1) are transformed into the corresponding 2-arylamino-1,3,4-oxadiazoles (5) or thiadiazoles (6) via reaction with phenyl isocyanate (or phenyl isothiocyanate), followed by brief treatment of the resulting adducts (2 and 3) with trifluoroacetic anhydride at ambient temperature. Treatment of compounds (1) with trifluoroacetic anhydride gave 2-trifluoromethyl-1,3,4-oxadiazoles (8)

Investigations on the structure of 4-methyldihydro-1,3,4-benzotriazepin-5-ones. Tautomer reassignment

The tautomerism of 4-methyldihydro-1,3,4-benzotriazepin-5-ones (2,3) is re-investigated by means of X-ray diffraction and quantum chemical calculations. The data revealed that the model compound (2a) exists in the amidrazone 1,4-dihydro tautomeric form (A), but not in the alternate 3,4-dihydro tautomer (B) as was previously reported.

Ring transformation of heterocycles. II: Ring contraction of 5,6-dihydro-4H-1,2,4,5-oxatriazines into 1H-1,2,4-triazoles

6-Monosubstituted 5,6-dihydro-4H-1,2,4,5-oxatriazines (3) undergo ring contraction, via elimination of H 2 O, to yield the respective 1H-1,2,4-triazoles (4). This transformation is envisaged to proceed via the ring-opened (E)-hydrazonoxime (5) which then suffers dehydrative cyclization. The process is acid-catalyzed and is thermally induced. Apparently, the driving force for this transformation is linked to the aromaticity of the triazole product

Synthesis and Chiroptical Properties of Some N-(2-Chloro-7-cyclopropyl-4,7-dihydro-4-oxo-thieno[2,3-b]pyridine-5-carbonyl) L-α-Amino Esters

Abstract A series of N-(2-chloro-7-cyclopropyl-4,7-dihydro-4-oxothieno[2,3-b]pyridine-5-carbonyl)-L-α-amino esters (5 ) have been prepared via the respective thieno[2,3-b]pyridinyl-5-carbonyl chloride (4). The CD spectra of the L-aliphatic (5a -d ) and L-aromatic (5e-g) a-amino acid derivatives display, in organic solvents, sign inversion of the measured Cotton effect (CE) bands. This chiroptical behaviour is probably associated with differences in conformational isomerism of either set. MS and NMR spectral data of the title compounds are presented.