Keywords: methacryloylthiosemicarbazide of isonicotinic acid, intramolecular heterocyclization, X-ray crystallography.Previously the synthesis was reported of β-N-(methacryloylcarbamothioyl)isonicotinohydrazide (1) which, on boiling in 2-propanol for 10-16 h, underwent intramolecular cyclization to give β-N-(5-methyl-4-oxo-5,6-dihydro-4H-1,3-thiazin-2-yl)isonicotinohydrazide (2) [1]. The objective of the present work includes the study of the reaction of thiosemicarbazide 1 with a series of amines with the aim of obtaining the corresponding products of nucleophilic addition at the activated C=C bond.However mixing compound 1 with equimolar quantities of cyclic secondary amines (morpholine, piperidine) or alkaloids (anabasine, cytosine) in ethanol or 2-propanol solutions at about 30°C gave not the expected addition products 3 but the product of heterocyclization of compound 1 -the substituted 5,6-dihydro-1,3-thiazin-4-one 2 in 82% yield. Under these conditions cyclization of compound 1 occurred considerably faster (~1 h) than the same reaction in boiling 2-propanol reported previously [1]. The yield of product 2 did not depend on either the structure or the basicity of the amine and alkaloid starting materials.It is probable that the presence of base in the reaction medium facilitates the formation of the thiol form of compound 1 which is necessary for its cyclization. The 1 H NMR and IR spectra of samples of compound 2 obtained by using various amines or on boiling in 2-propanol [1] were identical.

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The synthesis of some cytisine derivatives was carried out in the work. The article provides the data of quantum-chemical calculation and virtual screening of the alkaloid cytisine derivatives synthesized. At the same time, the reaction centers of the cytisine derivatives molecules were determined. In order to study the reactivity of the derivatives obtained (namely cinnamoylcytisine, lipoylcytisine, and cytisinylisoalantholactone) the quantum-chemical calculations were conducted to determine the energy and charge characteristics of the molecules. The results indicate a sufficient thermodynamic stability of the cinnamoylcytisine and lipoylcytisine molecules. The cytisinylisoalantholactone molecule is not stable according to the results of quantum chemical calculations. The data on the energy values of the frontier molecular orbitals show that, in general, all molecules exhibit electrophilic properties. A bioprediction was implemented using PASS (Prediction of Activity Spectra for Substances) as one of the most efficient and well-known computer program with the aim of detailed study and the probable establishment of the biological activity of the synthesized cytisine derivatives. Based on the results of virtual screening, promising types of alkaloid cytisine derivatives were identified, which are potential sources of original drugs