REVIEW for graduation qualification work (level / degree of education: master's degree, direction of training: "Chemistry") student of the Institute of Chemistry of St. Petersburg State UniversityMarchenko Sergey Alexeevich"Study of the spatial structure of triterpenoids and their derivatives by the NMR method" Graduation qualification work of Marchenko Sergey Alexeevich is a logical continuation of the research carried out for many years within the walls of the Institute of Chemistry of the St. Petersburg State University on establishing the structure and studying the intramolecular mobility of steroid systems by NMR spectroscopy. It is well known that the biological activity of chemical compounds depends on the spatial structure of the molecules. Consequently, experimental information on the spatial organization of biologically active structures makes it possible to effectively model the interaction of the substrate with the active center of the enzyme, which ultimately allows more rational use of time and resources for the development of new drugs. In this connection, the presented study aimed at establishing the spatial structure of triterpenoids and their derivatives by the NMR method is unconditionally an actual one.  The work is presented in a classical style and consists of an introduction, two chapters (a literature review and discussion of results), an experimental part, conclusions, a bibliography and an appendix, which presents several examples of graphical determination of cross-relaxation rates and various NMR spectra of the compounds studied. It contains 7 tables and 24 figures, greatly facilitating the perception of a fairly complex material and understanding the methodology of the study. In the literature review (Chapter 1) it is noted that the most common means of establishing the structure of triterpenoids until recently was the NMR spectroscopy method on 13C nuclei. In contrast to this approach, Sergey Alekseevich justifies the possibility of applying the results of the analysis of NMR spectra on 1H nuclei and the advantages of using the Overhauser nuclear effect (in comparison with structure-like steroids) and vicinal spin-spin interaction constants 3JH-H for the conformational analysis of triterpenoids. In Chapter 2, "Discussion of results" the results of an experimental study are described in detail and analyzed. Having chosen the 1H NMR method to establish the spatial structure of triterpenoids, Sergei Alekseevich faced the problem of identifying overlapping signals in the aliphatic region of these spectra. To solve the problem of full signal assignments in the 1H NMR spectra of the investigated compounds, the method of selective homonuclear decoupling of the scalar interactions 1H{1H}, which makes it possible to simplify the spin systems, as well as the correlation two-dimensional spectroscopy methods – DQF-COSY and NOESY, was most actively used. The next important stage in the establishment of the spatial structure of triterpenoids was the use of quantitative estimates of NOE and vicinal constants 3JH-H. It is important to note that, according to the obtained results, the use of an NMR spectrometer with an operating frequency of 300 MHz makes it possible to avoid the appearance of the dependence of the NOE on the parameter ωoτc on the nonlinear region, which makes it possible to correctly apply the calibration method of measuring distances. For compound (1a), NOESY spectra were recorded for experimental determination of cross-relaxation rates at different mixing times and under conditions of incomplete relaxation delay (Fast NOESY mode, PANIC approach). Furthermore, to improve the accuracy of interproton distances in axially symmetric triterpenoid molecules were corrected for anisotropic diffusion, calculated on the basis of an experimental evaluation of the anisotropy parameter D║/D┴ by comparing heteronuclear Overhauser effect in one of the methylene groups of the molecule. In the case of triterpenoid (1a), the comparison of the experimental and calculated interproton distances, as well as the comparison of the experimental and calculated vicinal constants, allowed the author to make a conclusion about the conformational rigidity of this molecule. At the same time, the use of a similar approach in the investigation of triterpenoid (2a) made it possible to establish the presence of a rapid (in the NMR time scale) two-position equilibrium in the solution, associated with a change in the conformation of the ring A, and to estimate the conformers ratio at room temperature. In the experimental part of the work, the conditions for obtaining and processing NMR spectra are given, as well as information on the computer programs used. There are no fundamental remarks on the peer reviewed work. In the text, there are a few typos: "стереоспицифических" (p. 7), "соединенениями" (p. 10), "циклогескановые" (p. 12), "муьтиплетные" (p. 16), "полущирина " (p. 26), instead of "T.P.E." (ref. 29 in p. 64) should be "Трифонов Р.Е."), which do not reduce the overall favorable impression of the work. Thus, the graduation qualification work presented by Marchenko Sergey Alekseevich fully meets the requirements for the work of such a profile, and deserves an "excellent" rating. Reviewer, Associate Professor of the Department of Organic Chemistry of Herzen State Pedagogical University of Russia, PhD in Chemistry  by specialty 02.00.03 - Organic Chemistry                                                   R.I. Baichurin