741 Recently, compounds containing triphenylmethyl or triindolylmethyl fragments have attracted the interest of researchers. This is due to the fact that some compounds of this type exhibit useful biological properties, such as antimicrobial and antiproliferative. 1–6 3,3-Bis(indol-3-yl)- 1,3-dihydroindol-2-ones obtained from isatins are com- pounds containing a diindolylphenylmethyl moiety. Representatives of this chemotype showed antitumor activity, which strongly depends on the presence of substi- tuents in the indole and oxindole rings. 7–13 The aim of this study was to examine the effect of the methyl group and the chlorine atom at different positions of the oxindole ring of 3,3-bis(indol-3-yl)-1,3-dihydroindol- 2-one on cytotoxic properties and also to try to improve their solubility in water by introducing a 3-dimethyl- aminopropyl group into the molecule. We synthesized 3,3-diindolyl-1,3-dihydroindol-2-ones 3a–g via the reaction of indoles 1a,b with the corre- sponding isatins 2а–g in the presence of AcOH according to the previously described method 14 (Scheme 1). The reaction is conveniently carried out by heating in MeOH under reflux with the addition of a small amount of AcOH. In this case, the reaction product usually precipitates upon cooling as small colorless crystals. The reaction rate depends on the type and position of the substituent in the starting isatin. Thus, 7-methylisatin reacts faster than 5-methylisatin, and longer heating is required to obtain the 4-methyl derivative. Despite the fact that a large number of methods for synthesizing structures of this type are described in the literature, 7,12,14 including sometimes quite exotic ones, 15–17 in general, these methods have no particular advantages over the conditions we employed 14 in the simplicity of implementation and the availability of reagents, as well as the yields and ease of isolation of the final product and demonstrate only the versatility of methods and approaches of organic chemistry. Some Chemistry of Heterocyclic Compounds 2020, 56(6), 741–746 Synthesis and study of cytotoxic activity of novel 3,3-bis(indol-3-yl)-1,3-dihydroindol-2-ones Sergey N. Lavrenov 1 *, Olga P. Bychkova 1 , Lyubov G. Dezhenkova 1 , Arthur S. Mkrtchyan 2 , Victor V. Tatarskiy 3,4 , Elena A. Tsvigun 1 , Alexey S. Trenin 1 1 Gause Institute of New Antibiotics, 11 B. Pirogovskaya St., Moscow 119021, Russia; e-mail: lavrenov@mail.ru 2 Volgograd State Technical University, 28 Lenina Ave., Volgograd 400005, Russia; e-mail: artur_mkrtchyan_96@inbox.ru 3 N. N. Blokhin Russian Cancer Research Center, 24 Kashirskoe shosse, Moscow 115478, Russia; e-mail: tatarskii@gmail.com 4 National University of Science and Technology MISiS, 4 Leninsky Ave., Moscow 119049, Russia; e-mail: tatarskii@gmail.com Submitted February 13, 2020 Accepted after revision May 12, 2020 A series of 3,3-bis(indol-3-yl)-1,3-dihydroindol-2-ones containing substituents at different positions of the oxindole ring were synthe- sized to study the effect of the position of the substituent on biological activity. Some of the new derivatives showed high in vitro cyto- toxic activity (MTT assay) on human tumor cell lines and lower (60 and 150 times less) cytotoxicity on donor human fibroblasts com- pared to doxorubicin. Keywords: 3,3-bis(indol-3-yl)-1,3-dihydroindol-2-ones, isatin derivatives, triarylmethanes, cytotoxic activity. In memory of Professor Maria Nikolaevna Preobrazhenskaya HN NH NH R O 0.2 0.1 1.6 IC 50 , μM Cancer cells (HCT116) Human fibroblasts 7-Me 7-Cl 6-Me 13.1 14.7 9.6 R Translated from Khimiya Geterotsiklicheskikh Soedinenii, 2020, 56(6), 741–746 0009-3122/20/56(6)-0741©2020 Springer Science+Business Media, LLC DOI 10.1007/s10593-020-02725-1