Previously, some diamides of malonic acid were obtained using carbon suboxide and pharmacologically investigated So at the disodium salt of N, N’-malonyl-bis-p-aminobenzoic acid coronary vasodilating, hypotensive properties were discovered and it was found a significant influence on a lipid metabolism. In connection with the use condensation reaction of malonic ester with anaesthesin in the inert solvent (kerosene at a temperature of more than 160°C) for obtaining of diamides of malonic acid it has been of interest to determine the structure of the basic components of the reaction shown in the scheme:formulaAccording to this scheme obtained compound IV is the main intermediate for the synthesis of various physiologically active salts of N, N'-malonyl-bis-p-aminobenzoic acid. Compounds III and IV have been isolated individually and characterized from elemental analysis data, TLC characteristics and melting points. However, this is not enough information to determine the structure of these substances. More information about the structure of III and IV have been obtained by UV, IR and NMR spectroscopy.Compound III: UV (EtOH) lmax 272 nm, (H2O) lmax 270 nm. Compound IV: UV (EtOH) lmax 279 nm. The IR - spectrum of III: vibrations at 3400 - 3200 cm-1 (n(NH) amide NHCO in trans-position, and the presence of hydrogen bonding), 3155, 3105 (vibrations of NH group in cis-position and mixed cis- and trans- hydrogen bonding), 1720 (n(C=O) ester group), 1660 (n(C=O) amide NHCO), 1600, 1475, 1450 (C=C planar vibrations of the aromatic ring), 1540 (d(NH) and n(CN) of amide), 1405 (d(C=O) of CH2CO), 1095 and 1240 (ns(C-O) and nas(C-O) of ester group), 1180, 1120, 1095, 1020, 850, 825, 760 (d(CН) – planar and out of planar deformation vibrations of 1,4disubstituted aromatic ring), 760 and 690 cm-1 (d(NHCO)). The difference in the intensity of the absorption bands of stretching vibrations n(C=O) in the range of 1660 - 1680 and 1715 – 1720 cm1 and n(NH) in the range of 3360 – 3290 cm-1 has allowed to conclude about quantity of amide and ester groups in the compounds III and IV (fig.). 1Н NMR data (400 MHz, DMSO, d, ppm): compound III: 1.21 – 1.18 (t, 3Н), 1.32 – 1.28 (t, 3Н), 3.49 (s, 2Н), 4.14 – 4.09 (q, 2Н), 4.31 – 4.25 (q, 2Н), 7.93 – 7.69 (m, 4Н arom), 10.50 (s, 1H); compound IV: 1.32 – 1.28 (t, 6Н), 3.56 (s, 2Н), 4.31 – 4.25 (q, 4Н), 7.93 – 7.72 (m, 8Н arom), 10.52 (s, 2H). Differences in NMR spectra of III and IV are that the intensity of the singlet 2H of -CO-CH2-CO- group is twice more for compound III than IV. Chemical shifts of hydrogens of two aromatic COOEt groups of compound IV coincide. The final structure of compound III was confirmed by X-ray diffraction analysis.figureFig. IR-spectra of compounds III and IV in the range 3600 – 3000 and 1800 – 1600 сm-1.