K. Pandiarajan

Synthesis and in vitro microbiological evaluation of novel 4-aryl-5-isopropoxycarbonyl-6-methyl-3,4-dihydropyrimidinones

Seven 4-aryl-5-isopropoxycarbonyl-6-methyl-3,4-dihydropyrimidin-2(1H)-ones 4a-g and 4-phenyl-5-isopropoxycarbonyl-6-methyl-3,4-dihydropyrimidin-2(1H)-thione 4h have been synthesized by a one-pot cyclocondensation of aldehydes, isopropyl acetoacetate and urea/thiourea in ethanol by using strontium chloride hexahydrate as the catalyst. All the compounds were screened for their antibacterial activity against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Salmonella typhi and antifungal activity against Candida albicans, Aspergillus flavus, Rhizopus and Mucor. Compounds 4b, 4c, 4f, 4g exhibited excellent in vitro antibacterial activity against Staphylococcus aureus, Salmonella typhi and Pseudomonas aeruginosa and potent in vitro antifungal activity against Candida albicans, Rhizopus and Mucor. Compound 4f with a nitro group at the para position of the 4-aryl group and 4g with a fluorine at the para position of the 4-aryl group showed more activity than the standard drugs.

Synthesis and anti-tubercular and antimicrobial activities of some 2r,4c-diaryl-3-azabicyclo(3.3.1)nonan-9-one N-isonicotinoylhydrazone derivatives

In this study, seven 2r,4c-diaryl-3-azabicyclo[3.3.1]nonan-9-one N-isonicotinoylhydrazones 8-14 were synthesized. The structure and stereochemistry of these compounds were established by IR and NMR spectral data. The purities were checked by elemental analysis. The synthesized compounds adopt twin-chair conformation with equatorial orientations of the aryl groups. The compounds were evaluated for their in vitro anti-tubercular and antimicrobial activities. The initial screen was conducted against Mycobacterium tuberculosis H(37)Rv (ATTCC 27294) and INH-TB by luciferase reporter phage assay method. All the synthesized compounds showed very good activity against MTB and INH-TB. Though all the compounds showed good antimicrobial activity only 11 (Ar = p-chlorophenyl), 12 (Ar = p-fluorophenyl), 13 (Ar = m-chlorophenyl) and 14 (Ar = m-methoxyphenyl) exhibited activity against all the tested (bacterial and fungal) microorganisms. The results suggest that the formation of hydrogen bonds may play a significant role in drug action.

Ethyl 6-r-(2-chlorophenyl)-2-oxo-4-phenyl­cyclohex-3-ene-1-t-carboxylate

In the title molecule, C21H19ClO3, the cyclohexene ring adopts an envelope conformation, with all substituents equatorial. The plane through its five coplanar atoms makes dihedral angles of 12.75 (14) and 74.16 (8)° with the phenyl and benzene rings, respectively. The dihedral angle between the latter two rings is 81.73 (12)°. Intermolecular C—H⋯O hydrogen bonds and intramolecular C—H⋯Cl contacts are found in the crystal structure; a weak C—H⋯π interaction is also present.

1-Methyl-3,5-bis-[(E)-(3-methyl-2-thienyl)methyl-ene]piperidin-4-one monohydrate.

In the title molecule, C18H19NOS2·H2O, the piperidine ring adopts an envelope conformation with the methyl substituent in an equatorial position. Each of the olefinic double bonds has an E configuration. The dihedral angle between the two thiophene rings is 6.04 (14)°. The water molecule forms two donor interactions, one with the carbonyl O atom and the other to the hetero N atom. The centrosymmetric {C18H19NOS2·H2O}2 pairs thus formed are linked into a supramolecular chain via C—H⋯Owater contacts.

c-5-Hy­droxy-r-2,c-4-bis­(meth­oxy­carbon­yl)-t-5-methyl-t-3-(3-nitro­phen­yl)cyclo­hexa­none

In the title compound, C17H19NO8 [systematic name = dimethyl 4-hydroxy-4-methyl-2-(3-nitrophenyl)-6-oxocyclohexane-1,3-dicarboxylate], the cyclohexanone ring exhibits a chair conformation. The methoxycarbonyl groups are oriented in opposite directions with respect to the cyclohexanone ring. In the crystal, O—H⋯O hydrogen bonds links the molecules into chains running parallel to the a axis. These chains are connected by weak C—H⋯O hydrogen bonds, forming sheets parallel to the ab plane.

(E)-N'-(3,3-Dimethyl-2,6-diphenyl-piperidin-4-yl-idene)isonicotinohydrazide.

In the title molecule, C25H26N4O, the piperidine ring adopts a chair conformation, with the plane through the four coplanar atoms making dihedral angles of 84.76 (6), 82.28 (5) and 81.91 (6)° with the pyridinering and the phenyl rings at the 2 and 6 positions, respectively. The pyridine ring makes dihedral angles of 64.13 (8) and 10.75 (8)° with the phenyl rings at the 2 and 6 positions, respectively. The dihedral angle between the two phenyl rings is 53.57 (8)°. The phenyl rings and one of the methyl groups at position 3 have an equatorial orientation. In the crystal, molecules are linked by N—H⋯O and C—H⋯O hydrogen bonds.

Ethyl 4-(4-bromo-phen-yl)-6-r-phenyl-2-oxocyclo-hex-3-ene-1-t-carboxyl-ate.

In the title compound, C21H19BrO3, the cyclohexene ring adopts an envelope conformation, with all substituents equatorial. The plane through its five coplanar atoms makes dihedral angles of 28.88 (10) and 71.94 (10)° with the bromobenzene and phenyl rings, respectively. The dihedral angle between the latter two rings is 51.49 (15)°. Intermolecular C—H⋯O hydrogen bonds are found in the crystal structure; a C—H⋯π interaction is also present.

2-Methyl-3,5,6-triphenyl-2,3-dihydro-pyrazine.

In the title molecule, C23H20N2, the heterocyclic ring adopts a screw-boat conformation, with all substituents equatorial. The phenyl ring at position 3 makes dihedral angles of 78.12 (15) and 72.67 (15)°, respectively, with the phenyl rings at positions 5 and 6; the dihedral angle between the phenyl rings at positions 5 and 6 is 67.32 (14)°. A C—H⋯π interaction is present in the crystal structure.

2,3,5-Triphenyl­pyrazine

In the title molecule, C22H16N2, the pyrazine ring deviates very slightly from planarity [maximum deviation 0.044 (3) Å], tending towards a twist-boat conformation. The phenyl ring at position 3 makes dihedral angles of 64.0 (2) and 45.8 (2)°, respectively, with the phenyl rings at positions 2 and 5. The dihedral angle between the phenyl rings at positions 2 and 5 is 49.7 (2)°. A C—H⋯π interaction is found in the crystal structure, but no classical hydrogen bonds form.

2-r-(4-Chloro-phen-yl)-6-c-phenyl-3,4,5,6-tetra-hydro-2H-thio-pyran-4-one 1-oxide.

The thiopyran unit of the title molecule, C17H15ClO2S, is in chair form. A crystallographic mirror plane bisects the molecule, passing through the O=S and the opposite C=O atoms of the central ring, with statistical disorder of the Cl atom. The geometry around the S atom is tetrahedral and the carbonyl C is planar. The 4-chlorophenyl group at the 2 position and the phenyl ring at the 6 position have equatorial orientations. Intermolecular C—H⋯O and C—H⋯Cl hydrogen bonds are found in the crystal structure. In addition, there is a short O⋯C intermolecular contact [2.970 (5) Å].