ORIGINAL ARTICLE Org. Commun. 11:3 (2018) 142-148 Synthesis and anticancer (MCF-7, PC-3) activities of new 2-hydroxy2,2-bis(4-substitutedphenyl)-N'-[(1E)-(3/4substitutedphenyl)methylene]-acetohydrazides İnci Selin Doğan *1, Hasan Erdinç Sellitepe 1, Nuran Kayıkçı Hande Sipahi 2, Rengin Reis 2 and Nurettin Yaylı 1 1 , 1 Faculty of Pharmacy, Karadeniz Technical University, 61080 Trabzon-Türkiye 2 Faculty of Pharmacy, Yeditepe University, 61080 Trabzon- Türkiye (Received June 29, 2018; Revised August 20, 2018 ; Accepted September 01, 2018) Abstract: A series of five –CH3, -NO2, -OCH3 and -Cl substituted 2-hydroxy-2,2-bis(4-phenyl)-N'-[(1E)-(3/4phenyl)methylene]acetohydrazide (1a-1e) was synthesized by the reaction of 2-hydroxy-2,2-diphenylacetohydrazide with substituted aromatic aldehydes to give intermediate Schiff bases. Structures of the synthesized compounds were characterized using NMR (1D; 1H, 13C/APT and 2D 1H-1H COSY, and NOESY), FT-IR, UV, LC-MS/MS spectral data and elemental analysis. The geometry of compounds 1a-1e were determined to be “E” by NOESY. All the tested compounds showed cytotoxic activity on MCF-7 and PC-3 cell line at highest experimental concentration (100 µM). Compounds 1b (18.24 ± 7.62 µM) and 1e (7.62 ± 1.85 µM) have strong anti-proliferative activity on MCF-7 cell line, while compound 1b (45.81 ± 1.10 µM) has the strongest activity on PC-3 cell line. Keywords: 2-Hydroxy-2,2-diphenylacetic acid; acetohydrazide derivatives; MCF-7; PC-3. ©2018 ACG Publication. All right reserved. 1. Introduction Carbon-carbon bond formation is the most important reaction for the synthesis of target molecules. Many of the carbon bond formation have been mentioned in the literature. 1-8 One of the most useful carboncarbon formation reactions is the benzoin reaction that is a promising method for the preparation of αhydroxyl diphenyl ketone.9,10 Diarylethanones and arylethanoic acids are important subunits and they have been found in a variety of natural products, which are important for the synthesis of pharmaceutical and agrochemical compounds. Benzil undergos a rearrangement to yield α-hydroxy acetic acid in the presence of a strong base. It could be converted to acetohydrazide and its derivatives to display biological activity due to the presence of potent pharmacophores.11-14 Moderate antibacterial activity of arylhydrazones of benzylic acid reacted with various aryl aldehydes has been mentioned.15 Recently, there has been considerable interest for the synthesis of substituted acetohydrazide and their thiazolidin-4-one derivatives. These compounds showed a broad biological activities such as anticancer12,16, antiviral17-21, anticonvulsant22, antimycobacterial23-25, cytotoxic26 and antifungal.27 Derivatives of acetohydrazide have already been reported to have anticancer or antitumor properties as kinase inhibitors.12, 16 Therefore, there is still need to synthesize and explore the pharmaceutical relevance of substituted acetohydrazides. Hence, herein, we disclose the synthesis of five new analogs of acetohydrazides and screen for their MCF-7 and P-3 human breast and prostate cancer activities, which displayed promising results. * Corresponding author: E-mail: isdogan@ktu.edu.tr The article was published by ACG Publications www.acgpubs.org/organic-communications July-September 2018 EISSN:1307-6175 DOI: http://doi.org/10.25135/acg.oc.47.18.06.107 Doğan et al., Org. Commun. (2018) 11:3 142-148 143 2. Experimental 2.1. Materials and apparatus All of the chemical reagents used in the synthesis were high grade of commercial products purchased from Sigma and used without further purification. The solvents (n-hexane, ethyl acetate, chloroform, diethyl ether, ethanol, methanol) were either analytical grade or bulk solvents distilled before use. Thin-layer chromatographies (TLC) were carried out on Merck pre-coated 60 Kieselgel F254 analytical aluminum acidic plates. Melting points were determined using Thermo-var apparatus fitted with a microscope and are uncorrected. 1H, 13C/APT and NOESY NMR spectra were recorded on a Bruker 400/100 MHz NMR with tetramethylsilane (TMS) as an internal standard, respectively. Infrared spectra were obtained with a PerkinElmer 1600 FT-IR (4000-400 cm-1) spectrometer. The mass spectral analyses were carried out on a Micromass Quattro LC-MS/MS spectrophotometer. The elemental analyses were performed on a Costech ESC 4010 instrument. 2.2. Methods The known sequential benzoin,9 benzil,10 2-hydroxy-2,2-diphenylacetic acid,11 ethyl-2-hydroxy-2,2diphenylacetate12,13,15 and 2-hydroxy-2,2-diphenylacetohydrazide15 syntheses (Scheme) were conducted according to the literature procedures. R O R OH OH H i, ii, iii OH OMe iv R R= -Cl, -CH3 O R R OH H N R R O H N O R1 H R O v OH NH NH2 R1 EtOH, 6 h R O 1a-1e Compounds 1a 1b 1c 1d 1e -R -Cl -Cl -Cl -Cl -CH3 -R1 p-Cl m-CH3 m-NO2 p-OCH3 m-CH3 Scheme. Chemical synthesis of 1a-e. (i) KCN, EtOH, reflux, 3 h; (ii) HNO3, reflux, 4 h; (iii) KOH, EtOH, reflux, 3 h; (iv) MeOH, H2SO4, reflux, 5 h; (v) H2NNH2.H2O, EtOH, reflux, 4 h. 2.2.1. General procedure for the synthesis of 2-hydroxy-2,2-bis(4-substitutedphenyl)-N'-[(1E)-(3/4substitutedphenyl)methylene]acetohydrazides (1a-1e) A mixture of substituted 2-hydroxy-2,2-diphenylacetohydrazide (6 mmol) and appropriately substituted benzaldehyde (6.6 mmol) was refluxed in absolute ethanol (30 mL) for 4 h. The reaction mixture was checked by TLC on silica gel plate. After the completion, the reaction mixture was cooled and excess 2-hydroxy-2,2-bis(4-substitutedphenyl)-N'-[(1E)-(3/4- substitutedphenyl)methylene]-acetohydrazides 144 ethanol was evaporated under reduced pressure. The resulting residue was allowed to stand overnight or, in some cases, refrigerated until it becomes solid which was then washed with water, dried and recrystallized from ethanol to give compounds 1a-1e. 2-Hydroxy-2,2-bis(4-chlorophenyl)-N'-[(1E)-(4-chlorophenyl)methylene]acetohydrazide (1a): Yield: 58%, white solid, Rf =0.87 (hexane-diethyl ether, 1:3), m.p. (oC): 219-220, IR (KBr, cm-1): 3340 (-OH), 3268 (NH), 3050 (=CH), 2950 (-CH), 1664 (-NHC=O), 1593 (-C=N), 1570, 1448 (-C=C- aromatic), 802 (-CCl), Anal. calcd for C21H15N2O2Cl3 (m.w.: 433.72): C, 58.15; H, 3.49; N, 6.46. Found: C, 58.33; H, 3.83; N, 6.46. LC-MS/MS: (m/z) (%) 434 (80), [M+H]+: 436 (65), [M+2H]+: 438 (15), [M+4H]+: 283(85) [MNHN=CHC6H4Cl]+. 2-Hydroxy-2,2-bis(4-chlorophenyl)-N'-[(1E)-(3-methylphenyl)methylene]acetohydrazide (1b): Yield: 52%, white solid, Rf =0.86 (ethyl acetate-hexane, 6:4), m.p. (oC): 273-274, IR (KBr, cm-1): 3338 (-OH), 3250 (NH), 3050 (=CH), 2950 (-CH), 1664 (-NHC=O), 1593 (-C=N), 1570, 1448 (-C=C- aromatic), 804 (-CCl), Anal. calcd for C22H18N2O2Cl2 (m.w.: 413.30): C, 63.93; H, 4.39; N, 6.78. Found: C, 64.79; H, 4.47; N, 6.82. LC-MS/MS: (m/z) (%) 414 (25), [M+H]+: 416 (45), [M+2H]+: 418 (17), [M+4H]+: 283(80) [MNHN=CHC6H4Cl]+. 2-Hydroxy-2,2-bis(4-chlorophenyl)-N'-[(1E)-(3-nitrophenyl)methylene]acetohydrazide (1c): Yield: 72%, light white solid, Rf =0.64 (ethyl acetate-hexane, 6:4), m.p. (oC): 189-191, IR (KBr, cm-1): 3345 (-OH), 3248 (-NH), 3050 (=CH), 2950 (-CH), 1664 (-NHC=O), 1593 (-C=N), 1570, 1448 (-C=C- aromatic, -NO2), 806 (-CCl), Anal. calcd for C21H15N3O4Cl2 (m.w.: 444.27): C, 56.77; H, 3.40; N, 9.46. Found: C, 56.59; H, 3.50; N, 9.38. LC-MS/MS: (m/z) (%) 443 (10), [M-H]+: 305(100) [M-NHN=CHC6H4Cl+Na-2H]+: 283(18) [MNHN=CHC6H4Cl]+. 2-Hydroxy-2,2-bis(4-chlorophenyl)-N'-[(1E)-(4-methoxyphenyl)methylene]acetohydrazide (1d): Yield: 77%, light brown solid, Rf =0.63 (ethyl acetate-hexane, 6:4), m.p. (oC): 187-190, IR (KBr, cm-1): 3346 (OH), 3265 (-NH), 3050 (=CH), 2950 (-CH), 1664 (-NHC=O), 1593 (-C=N), 1570, 1448 (-C=C- aromatic), 806 (-CCl), Anal. calcd for C22H18N2O3Cl2 (m.w.: 429.30): C, 61.55; H, 4.23; N, 6.53. Found: C, 61.49; H, 4.35; N, 6.66. LC-MS/MS: (m/z) (%) 428 (19), [M-H]+: 430 (15), [M+H]+: 438 (15), [M+4H]+: 288(100) [MC6H4Cl-OCH3+H]+. 2-Hydroxy-2,2-bis(4-methylphenyl)-N'-[(1E)-(3-methylphenyl)methylene]acetohydrazide (1e): Yield: 40%, brown solid, Rf =0.74 (ethyl acetate-hexane, 6:4), m.p. (oC): 180-182, IR (KBr, cm-1): 3319 (-OH), 3250 (NH), 3050 (=CH), 2950 (-CH), 1645 (-NHC=O), 1580 (-C=N), 1570, 1450 (-C=C- aromatic), 825 (pdisubs.), 734, 684 (p-disubs.), Anal. calcd for C24H24N2O2 (m.w.: 372.47): C, 77.39; H, 6.49; N, 7.52. Found: C, 77.13; H, 6.61; N, 7.45. LC-MS/MS: (m/z) (%) 373 (05), [M+H]+: 283(100) [M-C6H4CH3+2H]+. Table 1. 1H NMR data for the compounds 1a-1e*, DMSO-d6, 400 MHz (J= Hz) 1c 1d H 1a 1b 7.41, bs 7.41, bs 7.45, bs 7.61, d, J =7.6 2',6' 7.40, bs 7.45, bs 7.45, bs 7.69, d, J =7.6 3',5' 7.64, d, J =8.0 7.45, s 8.05, bs, J=3.0 7.05, d, J =8.0 2'' 7.48, d, J =8.0 7.03, d, J =8.0 3'' 7.21, d, J =7.2 8.26, d, J =7.4 4'' 7.48, d, J =8.0 7.30, d, J =7.2 7.70, t, J = 7.4 7.03, d, J =8.0 5'' 7.64, d, J =8.0 7.21, d, J =7.2 7.42, d, J =7.5 7.05, d, J =8.0 6'' CH=N 8.51, bs 8.48, bs 8.48, s 8.41, s NH 11.59, bs 11.59, bs 11.63, bs 11.81, bs -CH3 2.31, s, 3H -OCH3 3.81, s, 3H -CH3 *1H NMR data is assigned by the help of 2D-COSY and ACD NMR program. 1e 7.64, d, J=7.6 7.25, d, J =7.6 7.5, bs, J =3.0 7.39, m 7.39, m 7.63, m 8.51, s 11.72, bs 2.35, s, 6H 2.33, s, 3H Doğan et al., Org. Commun. (2018) 11:3 142-148 145 Table 2. 13C NMR data for the compounds 1a-1e*, DMSO-d6, 100 MHz. C 1a 1b 1c 1d 1 169.35 169.24 169.78 169.02 2 80.13 80.21 80.24 80.11 142.75 142.82 142.66 142.89 1' 128.26 128.25 128.29 129.00 2',6'’ 129.75 129.75 129.75 129.96 3',5' 135.04 134.64 132.94 132.73 4' 132.81 132.79 136.54 127.24 1'' 129.16 129.71 124.75 129.24 2'' 129.40 138.50 147.26 114.81 3'' 133.62 131.31 121.36 161.39 4'' 129.40 127.82 131.10 114.81 5'' 129.16 124.95 133.83 129.24 6'' CH=N 148.30 149.66 148.63 148.55 -CH3 21.31 -OCH3 55.75 *13C NMR data is assigned by the help of ACD NMR program. 1e 169.13 80.12 142.88 128.24 129.77 132.81 140.47 127.56 137.02 131.10 129.93 128.90 148.70 21.48 - 2.3. MCF-7 and PC-3 Assay (Cell viability) Cell viability was determined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay. MCF-7 human breast28 and PC-3 human prostate cancer cell lines29 (ATCC, USA) were seeded in 48-well plate and incubated for 24 h to form a semi-confluent layer. After 24 h, cells were exposed to four different concentrations of compounds (2, 10, 50 and 100 µM) dissolved in dimethyl sulfoxide (DMSO). After 24 h incubation, MTT was added to all wells at 0.5 mg/mL of concentration and incubated an additional 2 h at 37 °C. After discarding the medium from plates, 100 μl of isopropanol was added to the wells. Absorbance of the MTT formazan was determined at 570 nm by a UV-spectrophotometric plate reader (BioTek ELx808™, Turkey). Viability was defined as the ratio (expressed as a percentage) of absorbance of the cells exposed to compounds to the cells treated with 0.5% DMSO (as control). As a reference, doxorubicin HCl (Sigma-Aldrich, EP) was used. All the measurements were conducted in triplicates. 2.3.1. Statistical analysis GraphPad Prism 6 was used for all the statistical analyses. Data related to cell viability was analyzed by using one-way ANOVA following the post-hoc tests. Differences were considered as significant at p < 0.05. 3. Result and Discussion 3.1. Synthesis In this work, due to the biological evaluation, novel 2-hydroxy-2,2-bis(4-substitutedphenyl)-N'-[(1E)(3/4-substitutedphenyl)methylene]-acetohydrazides (1a-1e) were synthesized (Scheme). Substituted benzaldehyde was converted to benzoin by refluxing in ethanol in the presence of KCN. Benzoin was oxidized to benzil with HNO3. Alkali treatment of benzil yielded 2-hydroxy-2,2-diphenylacetic acid, which was then esterified and reacted with hydrazine hydrate in ethanol to give 2-hydroxy-2,2diphenylacetohydrazide. Finally, acetohydrazide compounds reacted with substituted aromatic aldehydes to give intermediate Schiff bases (1a-1e) in the range of 40-77% yields. All of the synthesized compounds (1a1e) were identified by spectroscopic methods such as 1D-NMR (1H, 13C/APT) and 2D-NMR (1H-1H COSY and NOESY), FT-IR, LC-MS/MS, elemental analyses and by the help of ACD NMR program. In the 1H NMR spectra (Table 1), the low-field signals of the amide group were observed at 11.5911.81 ppm, which resonate together to give a singlet (1a, 1b, and 1d). The aromatic protons of the p- 2-hydroxy-2,2-bis(4-substitutedphenyl)-N'-[(1E)-(3/4- substitutedphenyl)methylene]-acetohydrazides 146 substituted phenyl group of compounds 1a-1e form the characteristic AB-system (doublets H-2,6 and H-3,5 or bs). In the 1H NMR spectra of compounds 1a-1e, a characteristic singlet of azomethine proton at 8.48– 8.51 ppm was observed. The location of the azomethine (N=CH) proton signals at 8.48–8.51 ppm provided an opportunity to confirm the E/Z arrangement of the substituents around the double bond. The 2D NOESY spectra (Figure S1) showed correlation between amide –NH to azomethine (N=CH) protons, leading to an E geometrical isomer of all the synthetic compounds (1a-1e). The signals of the carbon at 148.30-149.66 ppm in the 13C NMR spectra (Table 2) were characteristic for azomethine (N=CH) carbon, which are an indication of hydrazine group of acetohydrazide (1a-1e). 3.2. Anticancer activity (MCF-7 and PC-3 Cell viability) Synthesized 2-hydroxy-2,2-bis(4-substitutedphenyl)-N'-[(1E)-(3/4-substituted-phenyl)-methylene]acetohydrazides (1a-1e) were evaluated for anticancer activity against MCF-7 and PC-3 in a concentration of 100 μM. IC50 values of the tested compounds on MCF-7 and PC-3 cell lines are given in Table 3. All the tested compounds showed cytotoxic activity on MCF-7 and PC-3 cell lines at the highest experimental concentration (100 µM). As seen in Figure S2, all the compounds showed statistically significant cytotoxicity compared to control group. Notably, compounds 1b and 1e have strong anti-proliferative activity on MCF-7 cell line, while compound 2 has the strongest activity on PC-3 cell line. In contrast to activity observed on MCF-7 cell line, compound 1e has the weakest inhibitory activity on PC-3 cell line compared to other derivatives. Figure 2 represents anti-proliferative activities of the compounds at the highest experimental dose (100 µM) on MCF-7 and PC-3 cell lines. 28-29 In the literature, various substituted carboxylic acid hydrazides compounds were reported to show selective cytotoxic activities toward cell lines of the NSC lung and breast cancers. Moreover, hydrazones inhibited the growth of ovarian cancer cell lines by 35.2–44.0%. But, it is mentioned that hydrazides of dicarboxylic acids were practically inactive compounds which had an antiproliferative effect against the cell line HS 578T of breast cancer. In our case, screening of the –Cl, –CH3, -NO2, and -OCH3 substituted 2hydroxy-2,2-bis(4-phenyl)-N'-[(1E)-(3/4-phenyl)methylene]acetohydrazide (1a-1e) against MCF-7 and PC3 cell lines revealed that –Cl and –CH3 substituted hydrazones 1b and 1e were found to be the best inhibitors against breast and prostate cancers. Table 3. IC50 values on MCF-7 and PC-3 cell line for compounds 1a-1e. Compounds 1a 1b 1c 1d 1e Doxorubicina a Reference compound. MCF-7 PC-3 IC50 (µM) ± SD 100 ≤ 18.24 ± 7.62 27.56 ± 5.66 43.13 ± 3.13 07.62 ± 1.85 0.065 ± 0.016 100 ≤ 45.81 ± 1.10 53.12 ± 5.41 90.17 ± 6.83 100 ≤ 2.96 ± 0.08 4. Conclusion In the present paper, synthetic procedure for the new 2-hydroxy-2,2-bis(4-substitutedphenyl)-N'-[(1E)(3/4-substitutedphenyl)-methylene]-acetohydrazide (1a-1e) was described and they were found to be very useful reactive intermediates of various N-heterocycles. Five synthesized compounds were tested for anticancer activity against breast and prostate cancer cell lines. This investigation showed that the most active compounds were 2-hydroxy-2,2-bis(4-methylphenyl)-N'-[(1E)-(3-methylphenyl)-methylene]acetohydrazide (1e) and 2-hydroxy-2,2-bis(4-chlorophenyl)-N'-[(1E)-(3-methylphenyl)-methylene]acetohydrazide (1b) on MCF-7 cell line, and 2-hydroxy-2,2-bis(4-chlorophenyl)-N'-[(1E)-(3-methylphenyl)methylene]acetohydrazide (1b) has the strongest activity on PC-3 cell line. Thus, compounds 1b and 1e would be useful for the development of new anticancer drugs against breast and prostate cancers. Doğan et al., Org. Commun. (2018) 11:3 142-148 147 Acknowledgements This study was supported by grants from Karadeniz Technical University Research Fund (KTU-BAP) of Turkey. Supporting Information Supporting information accompanies this paper on htttp://www.acgpubs.org/organic-communications ORCID İnci Selin Doğan:0000-0003-4949-1747 Hasan Erdinç Sellitepe:0000-0001-5339-6940 Nuran Kayıkçı :0000-0003-2864-2892 Hande Sipahi :0000-0001-6482-3143 Rengin Reis :0000-0002-3484-2201 Nurettin Yaylı :0000-0003-4174-3014 References [1] Trost, B. M.; Fleming, I. Comprehensive organic synthesis; Pergamon: New York, 1991, Vols. 1-9. [2] Sammelson, D. E.; Kurth, M. J. Carbon-carbon bond-forming solid-phase reactions. Part II, Chem. Rev. 2001, 101, 137-202. [3] Basavaiah, D.; Rao, A. J.; Satyanarayana, T. Recent advances in the Baylis-Hillman reaction and applications. Chem. Rev. 2003, 103, 811-892. [4] Huddleston, R. R.; Krische, M. J. Enones as latent enolates in catalytic processes: Catalytic cycloreduction, cycloaddition and cycloisomerization. Synlett 2003,1, 12-21. [5] Brahmachari, G. Design for carbon-carbon bond forming reactions under ambient conditions. RSC Advances 2016, 6, 64676-64725, [6] Umehara, A., Catalytic enantioselective carbon-carbon bond forming reactions of masked acyl cyanides. J. Synth. Org. Chem. Japan 2018, 76, 255-256. [7] Kool, E. T.; Breslow, R., Dichotomous salt effects in the hydrophobic acceleration of the benzoin condensation. J. Am. Chem. Soc. 1988, 110, 1596-1597. [8] Xin, L. H.; Potnick, J. R.; Johnson, J. S. Metallophosphites as umpolung catalysts: The enantioselective cross silyl benzoin reaction. J. Am. Chem. Soc. 2004, 126, 3070-3071. [9] Bhattacharya, A.; Purohit, V. C.; Beller, N. R. Benzoin condensation: Monitoring a chemical reaction by highpressure liquid chromatography. J. Chem. Educ. 2004, 81, 1020-1022. [10] Azizian, S.; Bafrooei, A. E.; Bashiri, H. Kinetics of catalytic oxidation of benzoin to benzil by alumina supported active MnO2, Kinet. Catal. 2010, 51, 244–249. [11] Braibante, M. E. F.; Braibante, H. T. S.; Uliana, M. P.; Costa, C. C.; Spenazzatto M. The use of benzil to obtain functionalized N-heterocycles. J. Braz. Chem. Soc. 2008, 19, 909-913. [12] Güzel, Ö.; Salman, A. Synthesis and biological evaluation of new 4-thiazolidinone derivatives. J. Enzyme Inhib. Med. Chem. 2009, 24, 1015-1023. [13] Güzel, Ö.; İlhan, E.; Salman, A. Synthesis and antimycobacterial activity of new 2-hydroxy-N-(3-oxo-1-thia4-azaspiro[4.4]non-4-yl)/(3-oxo-1-thia-4-azaspiro[4.5]dec-4-yl)-2,2-diphenyl-acetamid derivatives. Monatsh. Chem. 2006, 137, 795-801. [14] Safieh, K. A. A.; Al-Titi, A. M. S.; Zahra, J. A.; Ayoub M. T. Oxidative cyclization of arylidene carboxyhydrazides: Synthesis of substituted hydroxydiphenylmethyl-1,3,4-oxadiazoles. Jordan J. Chem. 2007, 2, 211-218. [15] Rollas, S.; Buyuktimkin, S.; Buyuktimkin, N.; Ulgen, M.; Yemni, E. Evaluation of some arylhydrazones of benzilic acid as antimicrobial agents. Pharmazie 1988, 43, 511-511. [16] Fahmy, H. T. Y. Synthesis of some new triazoles as potential antifungal agents. Boll. Chim. Farmaco 2001, 140, 422–427. [17] Rao, A.; Carbone. A.; Chimirri, A.; De Clercq, E.; Monforte, A. M.; Monforte, P.; Pannecouque, C.; Zappalá, M. Synthesis and anti-HIV activity of 2,3-diaryl-1,3-thiazolidin-4-(thi)one derivatives. Farmaco 2002, 57, 747-751. 2-hydroxy-2,2-bis(4-substitutedphenyl)-N'-[(1E)-(3/4- substitutedphenyl)methylene]-acetohydrazides 148 [18] Rao, A.; Balzarini, J.; Carbone, A.; Chimirri, A.; De Clercq, E.; Luca, L. D.; Monforte, A. M.; Monforte, P.; Pannecouque, C.; Zappalá, M. Synthesis of new 2,3-diaryl-1,3-thiazolidin-4-ones as anti-HIV agents. Farmaco 2004, 59, 33-39. [19] Barreca, M. L.; Chimirri, A.; Luca L. D.; Monforte, A. M.; Monforte, P.; Rao, M.; Zappalá, M.; Balzarini, J.; De Clercq, E.; Pannecouque, C.; Witvrouw, P. Discovery of 2,3-diaryl-1,3-thiazolidin-4-ones as potent antiHIV agents. Bioorg. Med. Chem. Lett. 2001, 11, 1793-1796. [20] Barreca, M. L.; Chimirri, A.; De Clercq, E.; Luca, L. D.; Monforte, A. M.; Monforte, P.; Rao, A.; Zappalá, M. Design and discovery of new potent RT inhibitors. Farmaco 2003, 58, 259-263. [21] Rao, A.; Carbone, A.; Chimirri, A.; De Clercq, E.; Monforte, A. M.; Monforte, P.; Pannecouque, C.; Zappalá, M. Synthesis and anti-HIV activity of 2,3-diaryl-1,3-thiazolidin-4-ones. Farmaco 2003, 58, 115-120. [22] Ragab, F. A.; Eid, N. M.; El-Tawab, H. A. Synthesis and anticonvulsant activity of new thiazolidinone and thioxoimidazolidinone derivatives derived from furochromones. Pharmazie 1997, 52, 926-929. [23] Babaoglu, K.; Page, M. A.; Jones, V. C.; McNeil, M.; Dong, C.; Naismith, J. H.; Lee, R. E. Novel inhibitors of an emerging target in Mycobacterium tuberculosis; substituted thiazolidinones as inhibitors of dTDPrhamnose synthesis. Bioorg. Med. Chem. Lett. 2003, 13, 3227-3230. [24] Bukowski, L.; Janowiec, M.; Zwolska-Kwiek, Z.; Andrezejczyk, Z. Some reactions of 2cyanomethylimidazo[4,5-b]pyridine with isothiocyanates. Antituberculotic activity of the obtained compounds. Pharmazie 1998, 53, 373-376. [25] Srivastava, T.; Gaikwad, A. K.; Haq, W.; Sinha, S.; Kati, S. B. Synthesis and biological evaluation of 4thiazolidinone derivatives as potential antimycobacterial agents. Arkivoc 2005, ii, 120-130. [26] Çoruh, I.; Rollas, S., Turan, S. Ö.; Akbuğa, J. Synthesis and evaluation of cytotoxic activities of some 1,4disubstituted thiosemicarbazides, 2,5-disubstituted-1,3,4-thiadiazoles and 1,2,4-triazole-5-thiones derived from benzilic acid hydrazide. Marmara Pharm. J. 2012, 16, 56-63. [27] Karali, N.; İlhan, E.; Gürsoy, A.; Kiraz, M. New cyclohexlidenehydrazide and 4-aza-1-thiaspiro[4,5]decan-3one derivatives of 3-phenyl-4(3H)-quinazolinones. Farmaco 1998, 53, 346-349. [28] Taha, M.; Shah, S. A. A.; Afifi, M.; Zulkeflee, M.; Sultan, S.; Wadood, A.; Rahim, F.; Ismail, N. H. Morpholine hydrazone scaffold: Synthesis, anticancer activity and docking studies. Chin. Chem. Lett. 2017, 28, 607-611. [29] Rodriguesa, B. S.; Ávilaa, R. I.; Benficaa, P. L.; Bringelb, L. P.; Oliveirab, C. M. A.; Vandresenc, F.; Silvad, C. C.; Valadaresa, M. C. 4-Fluorobenzaldehyde limonene-based thiosemicarbazone induces apoptosis in PC-3 human prostate cancer cells. Life Sci. 2018, 203, 141-149. © 2018 ACG Publications