A series of pyrazole and isoxazole derivatives were obtained by the condensation of the chalcones with hydrazine, phenylhydrazine, and hydroxylamine. All compounds were characterized using NMR, IR, and MS techniques. Chalcones are convenient intermediate compounds for the synthesis of five-, six-, and seven-membered heterocycles often exhibiting biological activity. Pyrazole and isoxazole derivatives constitute an interesting class of heterocycles due to their synthetic versatility and effective biological activities. Isoxazole derivatives represent a unique class of nitrogen-and oxygen-containing five-membered heterocycles, and they are associated with a wide spectrum of biological effects such as antiviral [1], anthelmintic [2], anti-inflammatory [3], anticonvulsant [4], anticancer [5], etc. Pyrazolines display various biological activities such as antimicrobial [6], antifungal [7], antidepressant [8], immunosuppressive [9], anticonvulsant [10], antitumor [11], antiamoebic [12], antibacterial [13], and anti-inflammatory [14]. β-Aminopropionic acid (β-alanine) is the simplest β-amino acid. It is the most important component of numerous biologically active compounds such as vitamin B 5 (pantothenic acid), penicillins, cephalosporins, and peptides [15]. The synthetic N-substituted β-alanines are growth stimulators for agricultural crops [16][17][18]. It is probable that the new compounds containing fragments of the above-mentioned compounds exhibit biological activity themselves.We continue our study of the chemistry of N-substituted amino acids and their derivatives. The starting compounds 1-3 were synthesized by condensation of N-(4-acetylphenyl)-β-alanine with aromatic aldehydes [19]. In this work, heating chalcones 1 and 2 under reflux with hydroxylamine in ethanol in the presence of sodium ethoxide gave disubstituted dihydroisoxazoles 5 and 6. Under different conditions, when pyridine was used as a base, we succeeded in synthesizing isoxazole derivative 7.In the IR spectrum of compound 7, the absorption band of the C=N group appeared at 1563 cm -1 . The 1 H NMR spectrum for compound 6 showed proton signals of the isoxazoline moiety as an ABX type spin system, and the proton signals were observed as double doublets due to the spin coupling. The signal of heterocyclic proton in compound 7 was observed at 7.02 ppm.

New 3-substituted 1-(3-hydroxyphenyl)-5-oxopyrrolidine derivatives containing hydrazone, azole, diazole, oxadiazole fragments, as well as 2-phenoxy- and 2,3-diphenoxy-1,4-naphthoquinone derivatives were synthesized. The structure of all compounds has been confirmed by NMR, IR, mass spectra, and elemental analysis data. Methyl 1-{3-[(3-chloro-1,4-dioxo-1,4-dihydro-2-naphthalenyl)oxy]phenyl}-5-oxo-3-pyrrolidinecarboxylate demonstrated potential antibacterial and antifungal activities as determined by diffusion and serial dilution methods, while N'-[(4-bromophenyl)methylidene]-1-{3-[(3-chloro-1,4-dioxo-1,4-dihydro-2-naphthalenyl)oxy]phenyl}-5-oxo-3-pyrrolidinecarbohydrazide and 2-{3-[4-(1,2,3-oxadiazol-5-yl)-2-oxo-1-pyrrolidinyl]phenoxy}-3-{3-[4-(1,3,4-oxadiazol-2-yl)-2-oxo-1-pyrrolidinyl]phenoxy}naphthoquinone showed antifungal activity against Candida tenuis and Aspergillus niger at low concentrations, as determined by the serial dilution method. The substitution of the methoxy fragment by N-containing substituents in monophenoxy substituted naphthoquinones was found to decrease their activity against Mycobacterium luteum. Besides, introduction of the second phenoxy substituted fragment increased the antifungal activity against Candida tenuis and Aspergillus niger at lower concentrations.

New N,N-disubstituted β-amino acids and their derivatives with thiazole, aromatic, and heterocyclic substituents were synthesized from N-phenyl-N-thiocarbamoyl-β-alanine by the Hantzsch method; derivatives with hydrazone fragments were also obtained. Some of the synthesized compounds exhibited discrete antimicrobial activity, and 3-[(4-oxo-4,5-dihydro-1,3-thiazol-2-yl)(phenyl)amino]propanoic acid was found to promote rapeseed growth and to increase seed yield and oil content.

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