The objective of the thesis is to build the synthesis process of Analogs of Bengamide A and E, conduct the biological activity of the synthesized Analogs. To find out more about the details of the content, please consult the thesis summary.
MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY - PHI THI DAO “ Synthesis and cytotoxicity of bengamide analogues A and E” Major : Organic Chemistry Code : 62 44 01 14 SUMMARY OF CHEMISTRY DOCTORAL THESIS HaNoi - 2018 The thesis was completed at: Graduated University of Science and Technology - Vietnam Academy of Science and Technology Scientific supervisor: Advisiors 1: Assoc Prof Dr Habil Van Cuong Pham Advisiors Dr Huong Doan Thi Mai 1st Reviewer: nd Reviewer: 3rd Reviewer: The thesis will be defended at Graduate University of Science and Technology - Vietnam Academy of Science and Technology, at hour date month 2018 Thesis can be found in: - The library of the Graduated University of Science and Technology, Vietnam Academy of Science and Technology - National Library of Vietnam Publications related to the thesis Thi Dao Phi, Huong Doan Thi Mai, Van Hieu Tran, Bich Ngan Truong, Tuan Anh Tran, Van Loi Vu, Van Minh Chau, Van Cuong Pham Design, synthesis and cytotoxicity of bengamide analogues and their epimers Med Chem Commun, 2017,8, 445-451 Thi Dao Phi, Huong Doan Thi Mai, Van Hieu Tran, Van Loi Vu, Bich Ngan Truong, Tuan Anh Tran, Van Minh Chau and Van Cuong Pham Synthesis of bengamide E analogues and their cytotoxic activity Tetrahedron Letters 2017, 58, 1830-1833 Phi Thi Dao, Doan Thi Mai Huong, Le Thi Phuong, Chau Van Minh, Pham Van Cuong Synthesis of 8-methyl-2-O-methyl-3,5-O-(1methyl ethylidene)-6,7,8,9-tetradeoxy-D-gulo-6-nonenonic acid (6E)- lactone Vietnam Journal of Chemistry, 2015,53 (2e), 154-157 Phi Thi Dao, Doan Thi Mai Huong, Vu Van Loi, Chau Van Minh, Pham Van Cuong Microwave-assisted synthesis of lactams from amino acids Vietnam Journal of Chemistry, 2015, 53 (2e), 198-201 Phi Thi Dao, Vu Van Loi, Nguyen Thi Bich, Doan Thi Mai Huong, Nguyen Hien, Chau Van Minh, Pham Van Cuong Synthesis of N-alkyl amino lactam derivatives Journal of Science and Technology, 2016, 54 (2C), 291-298 Phi Thi Dao, Doan Thi Mai Huong, Vu Van Loi, Chau Van Minh, Pham Van Cuong Synthesis and cytotoxicity of (2R,3R,4S,5R,6E)-3,4,5-trihydroxy-2-methoxy-8,8-dimetyl-N-((S)-2oxoazepan-3-yl)non-6-enamide Vietnam Journal of Chemistry, 2016, 54 (6e2),62-65 Phi Thi Dao, Doan Thi Mai Huong, Vu Van Loi, Nguyen Thii Hue, Pham Van Cuong In vitro cytotoxic and antimicrobial activities of some bengamide derivatives Vietnam Journal of Chemistry 2017 55(3), 342-347 Patent for utinity solution Synthetic method of bengamide analogues Accepted application I INTRODUCTION Introduction Natural compounds isolated from terrestrial plants have been studied for a long time and have been successful However, studies on marine compounds have only begun in the middle of the last century Currently, natural marine compounds are known to be a promising source of pharmaceuticals, and many highly biologically active compounds have been found in various marine organisms Difficulties in collecting large amounts of samples and requiring high funding are one of the obstacles to research in the field of marine chemical compounds Therefore, organic synthesis is an effective alternative to generate larger amounts of active ingredients to serve biological studies, as well as to ensure their applicability Many marine-derived active compounds play as lead compounds so that researchers can make new derivatives possess higher biological activity The bengamides isolated from marine sponges are known for their potent anti-cancer activity However, structural instability is one of the reasons limiting the applicability of this class In order to overcome this limitation of bengamides, we chose the research topic "Synthesis and cytotoxicity of bengamide analogues A and E" in this thesis Objectives of the thesis - Constructing synthesis process of bengamide analgoues A and E - Evaluating the biological activity of the synthesized analogs Scientific significance and new contribu, 1,4-dioxane, sodium-2 ethylhexanoate Applying the lactone ring-opening reaction of ketide BG5 with the aminolactam under microwave irradiation conditions as described above, the acetonide BG40a-d was also synthesized Compound BG5 when reacted with rac-BG22a (3S*, 6S*) racemic mixture forms two codiastereomer BG40a and BG40b The two diastereomers BG40a and BG40b were separated by preparative thin layer chromatography The chemical structures of the BG40a-d compounds were confirmed by spectral analysis, especially NMR spectra The formation of an amide bond between the ketide chain and the aminolactam portion was demonstrated by the interaction of C-1 with H-2' proton, and the interaction of amide proton (NH-13) with C-1 and C-1' on the HMBC spectrum Comparison of NMR data and optical rotation with bengamide Y allows to determine 2'S, 5'S configuration of compound BG40a Thus, 2'R, 5'R configuration is assigned to the remaining BG40b Similarly, the reaction between BG5 and the racemic mixture rac-BG22b (3S*, 6S*) yielded two diastereomers BG40c and BG40d by preparative thin layer chromatography 2'S, 5'R configuration was determined for BG40c and 16 2'R, 5'S configuration for BG40d was based on the comparison of NMR data and optical rotation with previous publication Figure 3.39 Major interactions of BG40a on COSY and HMBC spectrum Similar to the bengamide E analogues, the analogues of bengamide A were synthesized by the removal of the acetonide group of compounds BG40a-d in the presence of TFA and THF at 0-5°C for h Comparison of NMR data of BG41a-d with acetonides BG40a-d revealed that the disappearance of two methyl groups and one quaternary carbon confirmed the removal of the acetonide group 3.5 Synthesis of fluorine containing bengamide analogs In order to understand the role of terminal olefinic part to the biological activities of bengamides, we have synthesised and investigated 17 the biological activity of the analogue in which the terminal olefinic part is replaced by CH(OH) -CH2F group The process of synthesizing these analogs was carried out as described in Figure 3.45 Figure 3.45: Synthesis of fluorine containing bengamide analogs The synthetic process of fluorine containing bengamide analogs was first performed by the fluorinated reaction of compound BG3 with diethylaminosulfur trifluoride (DAST) at room temperature to obtain the BG3F in 42% This fluorination occurs selectively at the primary hydroxyl group The structure of was confirmed by analysis of spectral data The HRESI-MS of BG3F appeared at at m/z 263.0928 [M-H]- being suitable to the expected formula C11H16FO6 of BG3F In addition, the presence of fluorine in the structure of BG3F also expressed by the double signals induced by interaction of C-7 [δC 83.7 (d, JC-F = 166.25 Hz)], C-6 [δC 68.6 (d, 2J C-F = 18.75 Hz)] and C-5 [67.0 (d, 3J C-F = 6.25 Hz)] with the fluorine atom The fluorine BG3F derivative was then reacted with the abovedescribed aminolactams, in the presence of sodium 2-ethylhexanoate under microwave irradiation conditions at 100 W for hour obtained the 18 corresponding lactone ring-opening product Its chemical structure has also been confirmed by spectral methods, particularly by the HMBC spectrum In particular, the connection of the aminolactam ring and the polyketide chain was confirmed by the interaction of C-1, C-2 and C2’ with NH proton of the formed amide group Figure 3.50 Major interactions on COSY and HMBC spectrum of BG4Fa and BG4Fb Similar to the removal of the acetonide group in the synthesis of the bengamide A analogues described above, the deprotection of acetonide group of BG4Fa was carried out in the presence of TFA in THF, at 0oC to room temperature However, under these reaction conditions, the starting material was decomposed and the desired product was not observed Change of TFA into a solution of 1N HCl provided the desired product Accordingly, BG4Fa was obtained with a yield of 33-50% in THF for 24 hours Meanwhile, the use of MeOH instead of THF lead to BG4Fa in 19 higher yield (58 - 66%) and shorter time (5 hours) It can be observed that the use of HCl 1N in MeOH is more suitable for the removal of the acetonide group of the fluorine containing analogue bengamide 3.6 Biological activities of synthesized analogues 3.6.1 Cytotoxic activity All synthetic analogues were evaluated for their cytotoxicity against a panel of cancer cell lines (KB, HepG-2, LU-1, MCF-7, HL-60 and Hela) Cytotoxicity comparision of the tested compounds revealed that the 2’R series were generally more cytotoxic than the corresponding 2’Sepimer which possessed similar C-2’ configuration as the natural bengamides (Table 3.13) The analogues with 7-membered aminolactam rings are almost more active than the 6-membered ones These synthetic analogues were found to be less active against HL-60 and Hela cell lines in comparison with the other tested cell lines (KB, HepG-2, Lu-1 and MCF-7) Nine compounds, BG34b, BG35a, BG35b, BG36b, BG37b, BG38a, BG38b, BG39a and BG39b exhibited cytotoxic activity on all six cancer cell lines In particular, compound BG36b exhibited strong cytotoxic activity against six cancer cell lines KB, HepG-2, LU-1, MCF7, HL-60 and Hela with IC50 value of 1.1, 1.1, 0.5, 0.2, 5.4 and 2.3 μM, respectively On the other hand, compounds BG36a and BG36b exhibited selective cytotoxic activity against MCF-7 breast cancer cell 20 lines with IC50 values of 1.3 and 0.2 μM, while compounds BG37b and BG38b selectively inhibited against three cancer cell lines (KB, HepG-2 and LU-1) with an IC50 value in the range of 0.3-1.1 μM Beside that, compounds BG39a and BG39b exhibited selectively against KB and HepG-2 cancer cell lines with IC50 value of 0.4 and 1.9 μM Table 3.13 Result of cytotoxic activity of synthetic bengamide analogues IC50 (µM) Analog KB HepG-2 Lu-1 MCF-7 HL-60 Hela BG32a 22.1 >50 13.8 >50 >50 >50 BG32b 11.1 22.0 2.6 >50 >50 >50 BG33a 8.2 11.8 12.7 20.1 >50 >50 BG33b 2.4 6.6 2.6 8.8 >50 >50 BG34a 2.9 11.3 7.5 17.8 >50 39.7 BG34b 4.4 12.0 2.7 20.4 29.0 19.7 BG35a 2.3 6.6 5.8 4.3 36.8 36.8 BG35b 1.7 2.4 2.3 15.1 21.5 16.1 BG36a 21.0 21.1 4.3 1.3 >50 >50 BG36b 1.1 1.1 0.5 0.2 5.3 2.1 BG37a 11.8 >50 17.1 >50 >50 >50 BG37b 0.4 1.0 0.3 10.4 19.5 39.1 BG38a 5.7 4.8 7.7 32.5 45.6 41.5 BG38b 1.0 1.9 1.1 8.6 10.6 16.2 21 IC50 (µM) Analog KB HepG-2 Lu-1 MCF-7 HL-60 Hela BG39a 1.9 1.5 23.6 4.9 13.4 26.9 BG39b 1.1 0.4 25.1 2.7 8.9 9.5 BG41a 19.8 >50 10.0 >50 >50 >50 BG41b 5.1 21.3 17.2 >50 12.1 15.4 BG41c >50 >50 23.4 23.4 >50 >50 BG41d 23.7 >50 36.3 >50 >50 >50 BGF5a >50 >50 >50 >50 >50 >50 BGF5a >50 >50 >50 >50 >50 >50 Elipticine 1.2 1.6 1.2 2.4 2.0 1.6 Positive control: Elipticine Compounds with hydroxyl group at 5'-position exhibited lower activity than analogs without OH groups at the lactam ring Among these compounds, the two compounds BG41a and BG41b exhibited significant activity against Lu-1 and KB cell lines The remaining two compounds showed no significant activity against all six cancer cell lines On the other hand, the two fluorine compounds BG5Fa-b did not show cytotoxic activity against the six cancer cell lines In addition, the remaining fluorine compounds (BG7Fa-b, BG9Fa-b, BG11Fa-b, BG13Fa-b) were also tested against six other cancer cell lines, NCIH1299, A549, MCF-7, MDA-MB-231, Hep3B and Hela However, all of these compounds are not active This suggests that the olefinic terminal structure plays an important role in cytotoxic activity In addition, in order to understand the flexibility effects of the ketide side chain and free hydroxy groups at C-3, C-4 and C-5 to cytotoxic activity, some acetonide compounds BG24a, BG28a-b and BG31a-b have also been tested for 24 Gram (+) strains such as BG32a, BG34b, BG35b, BG38b and BG39b In addition, the BG35b and BG39b compounds exhibited good activity against Candida albicans This is the first study of the antimicrobial activity of bengamide compounds The evaluation of structure - activity relationships showed that the C-2’R series showed better activity than the corresponding 2'S epimer which represented similar configuration at C-2’ as natural bengamides This is the first time the benamide analogues with the C-2'R configuration have been synthesized and investigated biologically Biological comparison between diastereomer isomers is very interesting and these results could contribute to the basis for further research orientations to find more bioactive compounds of this class Cytotoxic activity demonstrates that fluorine containing analogues are not active against all of tested cancer cell lines Futhermore, the acetonide compounds are much less active than their corresponding acetonide deprotection analogues This observation pointed out that the olefinic structure, the tert-butyl group, the presence of three free hydroxyl groups at C-3, C-4 and C-5, and their flexibility play an important role to the cytotoxic activity of bengamides ... 16 analogues of bengamide E, analogues of bengamide A and 10 analogues containing fluorine During the synthesis of these compounds, many reaction steps were optimized and provided better yields... the removal of the acetonide group in the synthesis of the bengamide A analogues described above, the deprotection of acetonide group of BG4Fa was carried out in the presence of TFA in THF, at... (Table 3.13) The analogues with 7-membered aminolactam rings are almost more active than the 6-membered ones These synthetic analogues were found to be less active against HL-60 and Hela cell