New insights in the discovery of novel h-MAO-B inhibitors: structural characterization of a series of N-phenyl-4-oxo-4H-chromene-3-carboxamide derivatives

The synthesis, crystal structure and Hirshfeld analysis of 4-(3,4-di-methyl-anilino)-N-(3,4-di-methyl-phen-yl)quinoline-3-carboxamide

The structure of the title quinoline carboxamide derivative, C26H25N3O, is described. The quinoline moiety is not planar as a result of a slight puckering of the pyridine ring. The secondary amine has a slightly pyramidal geometry, certainly not planar. Both intra- and inter-molecular hydrogen bonds are present. Hirshfeld surface analysis and lattice energies were used to investigate the inter-molecular inter-actions.

Isolation of intermediates in the synthesis of new 3,4-dihydro-2H-chromeno[2,3-d]pyrimidines

Reaction ofN-alkyl-2-imino-2H-chromene-3-carboxamides with dimethyl acetylenedicarboxylate (DMAD) in the presence of sodium carbonate as catalyst in refluxing ethanol gave new tricyclic products identified as methyl 3-alkyl-2-(2-methoxy-2-oxoethyl)-4-oxo-3,4-dihydro-2H-chromeno[2,3-d]pyrimidine-2-carboxylates. In the absence of sodium carbonate, dimethyl 2-((E)-3-(alkylcarbamoyl)-2H-chromen-2-ylideneamino)fumarates were isolated as intermediates. These intermediates could be successfully converted to the same new tricyclic products by heating in ethanol containing sodium carbonate. All new synthetic compounds were characterized on the basis of their FT-IR,1H and13C NMR spectra, and microanalytical data. To identify the correct stereoisomer of the intermediates, in one case a 2D nuclear Overhauser effect (2D-NOESY) spectrum together with density functional theory (DFT) calculation at the B3LYP/6-311+G(d,p) level of theory was used.

Synthesis of new 3H-chromeno[2,3-d]pyrimidine-4,6(5H,7H)-diones via the tandem intramolecular Pinner/Dimroth rearrangement

The reaction of 2-amino-4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles with excess aliphatic carboxylic acids in the presence of phosphoryl chloride (POCl3) afforded new 2-alkyl-5-aryl-8,8-dimethyl-8,9-dihydro-3H-chromeno[2,3-d]pyrimidine-4,6(5H,7H)-diones in high yields. The suggested mechanism involves a tandem intramolecular Pinner/Dimroth rearrangement. The synthesized compounds were characterized by infrared (IR), proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR) and elemental analysis.

A comparison of the structures of some 2- and 3-substituted chromone derivatives: a structural study on the importance of the secondary carboxamide backbone for the inhibitory activity of MAO-B

The crystal structures of the 3-substituted tertiary chromone carboxamide derivative, C17H13NO3, N-methyl-4-oxo-N-phenyl-4H-chromene-3-carboxamide (1), and the chromone carbonyl pyrrolidine derivatives, C14H13NO3, 3-(pyrrolidine-1-carbon-yl)-4H-chromen-4-one (3) and 2-(pyrrolidine-1-carbon-yl)-4H-chromen-4-one (4) have been determined. Their structural features are discussed and compared with similar compounds namely with respect to their MAO-B inhibitory activities. The chromone carboxamide presents a -syn conformation with the aromatic rings twisted with respect to each other [the dihedral angle between the mean planes of the chromone system and the exocyclic phenyl ring is 58.48 (8)°]. The pyrrolidine derivatives also display a significant twist: the dihedral angles between the chromone system and the best plane formed by the pyrrolidine atoms are 48.9 (2) and 23.97 (12)° in (3) and (4), respectively. Compound (3) shows a short C-H⋯O intra-molecular contact forming an S(7) ring. The supra-molecular structures for each compound are defined by weak C-H⋯O hydrogen bonds, which link the mol-ecules into chains and sheets. The Cambridge Structural Database gave 45 hits for compounds with a pyrrolidinecarbonyl group. A simple statistical analysis of their geometric parameters is made in order to compare them with those of the mol-ecules determined in the present work.