The reaction of 16,16-dimethyl-8-aza-D-1,3,5(10),13-tetraene-12,17a-dione (3,3-dimethyl-3,4,6,7,11b, 12-hexahydro-1H-[2.1-a]1,13(2H)-dione) with hydroxylamine and methoxyamine in ethanol gives the 12-methoxyamino and 12-methoxyamino derivatives. The 12-hydroxyamino derivative was also obtained by the reaction of this 12,17a-dione with hydroxylamine hydrochloride and subsequent cleavage of the hydrochloride salt of the 12-hydroxyamino derivative by the action of base. The 12-methoxyamino derivative was obtained by the methylation of the 12-hydroxyamino derivative using methyl iodide in the presence of sodium methylate. Further evidence for the structures of the derivatives obtained was obtained using COSY, NOESY, HMBC, and HMQC NMR spectroscopy.

Intermolecular interactions in 2,3-dimethoxy-8-azagone-1,3,5(10),13-tetraene-12,17-dione and the molecular and crystal structure of this compound were studied by IR spectroscopy and x-ray diffraction analysis. Shortened intermolecular contacts related to the C-H⋯O, C-H⋯π, and π⋯π interactions were revealed in crystals of this 8-azasteroid. These contacts manifest themselves in changes in the characteristic frequencies of C-H, C=O, and C=C vibrations in the IR spectra. A relationship between the intermolecular interactions occurring in the crystalline and noncrystalline solid phases and the changes in the IR spectra of this compound was established.

Crystalline modifications of 8-aza-D-homogon-1,3,5(10),13-tetraen-12,17a-dione have been investigated by IR spectroscopy and x-ray structural analysis. It is shown that this compound crystallizes from solutions of chloroform with hexane in the form of a solvate comprised of chelate hydrogen bonds between the hydrogen atom of the chloroform molecule and the oxygen atoms of the carbonyl groups of the 8-azasteroid molecule. A relation between the changes in the characteristic absorption bands of the CH2-, C=O-, and I=C groups and the structure of the crystalline modifications has been established.

A new approach (AB + D → ABCD) to the construction of tetracyclic 8-azagonane (cyclopenta[5,6]pyrido[2,1-a]isoquinoline or benzo[a]cyclopenta[f]quinolizine) structures was developed and exemplified by cyclocondensation of 1-alkyl-3,4-dihydroisoquinolines with ethyl 2-oxocyclopentanecarboxylate.

By the method of IR Fourier spectroscopy with the use of numerical differentiation of spectral line profiles we have studied the spectra of some structural and functional derivatives of immunotropic 8-azasteroids in the region of C=O and C=C bonds (1800–1400 cm −1 ). We have established the dependence of vibration frequencies of the C=O and C=C groups on the size of the ring D , the presence of heteroatoms (O, S) in the ring D , transformations in the α-acyl-β-aminovinylcarbonyl fragment and in its adjacent positions of the heterosteroid skeleton, and the composite character of the absorption bands that are due to the vibrations of the C=O and C=C groups. The role of the structural and stereoelectronic factors in the observed group frequencies of 8-azasteroids is discussed.

Using the semiempirical method of partial neglect of differential overlap (PNDO), we have calculated the wave functions, energies, orbital configurations of electronic states, oscillator strengths of transitions, electronic density distributions, and dipole moments for the molecule of biologically active 8–azagona–12,17–dione, containing a conformationally rigid α–acyl–β–aminovinylcarbonyl fragment. It has been established that as to their orbital nature the excited lower and higher singlet electronic states of this molecule are of the n π * – and ππ * type respectively. The results of the theoretical analysis are in good qualitative agreement with the spectral data on absorption and luminescence. The calculations of the intermolecular interaction of the compound under consideration with a medium show that the molecular systems under consideration can possess a dynamic multicenter structure.

Biologically active molecules of 8-azagon-12,17-dion fluoresce in solvents of various natures, in the crystalline phase, and under conditions of high-temperature vapor. Characteristics of absorption and fluorescence of these molecules in aprotic acetonitrile are studied in detail. Absorption observed in the region of 250–400 nm is associated with transitions of the types π → π * and n → π * . Fluorescence excitation spectra demonstrated dependence of emission detected on the wavelength. Experimental data are analyzed within the framework of concepts of the multicentered nature of molecular systems on the basis of the model of electronic mesomeric tautomerism.

The IR spectra of biologically active molecules of 8-azasteroids and model compounds in the region of C=O, C=C, C--N, and C--H vibrations (1800–1400 cm −1 ) have been studied in detail. The structure of compounds containing isostructural and isoelectronic α--acyl--β--aminovinylcarbonyl and α--acyl--β--alkoxyvinylcarbonyl fragments have been analyzed. Interpretation of the structure of the IR spectra and of the specificity of the manifestation of the vibrational modes under consideration in the molecules of a particular class of 8-azasteroids is given. The electronic structure of the molecules under investigation complies with the model of mesomeric tautomerism of the aminovinyldicarbonyl fragment.

Different intermolecular compounds of 6,6'‐dimethyl‐2,3,4,5,6,7‐hexahydrobenzo[b]furan‐3,4‐dione have been investigated by IR spectroscopy and x‐ray structural analysis methods. The relation between changes in the characteristic absorption bands of CH2, CH3, C=O, and C—O—C groups and the properties of the medium surrounding the molecule is established. Crystals of monoclinic syngony, of space group P21/n, are formed from a chloroform‐hexane mixture in crystallization. In the crystalline structure, shortened intermolecular contacts between the atoms of hydrogen of the CH3 and CH2 groups of cyclohexane cycles and the oxygen atom of the furan cycle, and also between the atoms of hydrogen of the CH2 and CH3 groups of both cycles and the oxygen of the cyclohexane cycle are revealed.

The specific fluorescence properties as well as picosecond transient absorption features have been studied for two 8-azasteroids. It is shown that at various excitation wavelengths the essentially different final excited electronic states are realized. Because of the multicenter character of 8-azasteroids the spectroscopic data obtained may be analyzed on a basis of the “mesomeric tautomerism” model taking into account the dynamic combination of cis- and trans-configurations. The dependence of fluorescence spectral characteristics on the solvent nature is a manifestation of intermolecular H-bond interactions.

Luminescence of microcrystals of 2,3-methoxy-8-azagon-1,3,5(10),13-tetraene-12,17-dion of the class of molecules of biologically active steroids is detected at room temperature (293 K). It represents fast fluorescence of free and self-localized excitons and prolonged phosphorescence of triplet excitons.

Experiments on observation of the luminescence of 8-azasteroid derivatives and its regularities are carried out for the first time. Strong solvent and excitation wavelength dependences are observed for fluorescence spectra of the compounds investigated, whereas their fluorescence excitation spectra depend only weakly on the fluorescence emission wavelength. An analysis of the data obtained points to the complex character of the electronic structure, important role of intramolecular dynamics, and multicenter character of the behavior of these systems upon absorption of light.

The influence of cis-diamminedichloroplatinum(II) (cis-DDP) and trans-diamminedichloroplatinum(II) (trans-DDP) binding on the helix-coil transition of DNAs with different GC composition is investigated experimentally and theoretically (26% ≤ GC ≤ 72%; 0.003 ⩽ rb ⩽ 3; where rb is the number of moles of bound DDP per mole of nucleotide). In contrast to previous studies, it is demonstrated that cis-DDP increases the DNA melting temperature (Tm) if GC content and rb are low enough. Stabilization occurs for rb = 0.003 if GC = 26% or 42%. Destabilization takes place for higher GC and rb values. Trans-DDP causes only stabilization independently of GC content if rb ⩽ 0.3. For the highest GC content (72%), very low concentration rb = 0.003) of both compounds gives rise to a strong shift of the melting temperature which is equal to −4.5°C for cis-DDP and +3.5°C for trans-DDP. It is shown that well known bidentate and monodentate, kinetically inert platinum binding cannot bring about such a strong Tm alteration. Computer simulation of the helix-coil transition of DNA-ligand complexes is used to explain the observed effects.

A new method was developed for synthesis of fused nitrogen-containing heterocycles by cyclocondensation of alpha-hydroxymethylene ketones with cyclic azomethines.