Amides and hydrazides of aroylpyruvic acids. 2. Synthesis and biological activity of some arylidenehydrazides of aroylpyruvic acids

As shown in the previous communication [12], substituted amides and/3-acylhydrazides of aroylpyruvic acids are characterized by a wide spectrum of biological activity. These compounds possess antimicrobial [6, 12], antiviral [12], antiinflammatory, analgetic [4, 12], and antispasmodic [7] activity, and also may be used in the synthesis of dyestuffs, pesticides, and a variety of nitrogen-containing biologically active compounds [5]. While amides [2, 3] and acylhydrazides of the aroylpyruvic acids [12, 14] are sufficiently well known, the structurally-related methylenehydrazides have practically not been studied. We are aware of only a limited number of works [9, 11, 15, 20] containing fragmentary information on the synthesis of some compounds of this series. Biological activity of the methylenehydrazides of aroylpyruvic acids has not been reported before. In a search for biologically active compounds among the substituted hydrazides of the aroylpyrivic acids, we prepared the arylidenehydrazides of aroylpyrivic acids (I-XII) by the reaction of 5-aryl-2,3-dihydro-2,3-furandiones with the hydrazones of aromatic aldehydes and ketones in tetrahydrofuran or dioxane at room temperature. The constants and spectral characteristics of compounds I-XII are given in Table 1. Judging by the presence in the IR spectra of I-XII of a low-frequency band at 1590-1636 cm- 1, corresponding to the carbonyl groups of the/3-diketone fragment, these compounds exist in the form of the H-chelate with the stable intramolecularly hydrogen bond (IHB) of the type OH-.-O=C [18]. This fact agrees well with literature data indicating that/3-aroylhydrazides of aroylpyruvic acids are found in the enol chelate form of the carbonyl in position 2 [12, 14, 15].