organic papers Acta Cryst. (2006). E62, o1575–o1577 doi:10.1107/S1600536806010282 Akkurt et al.  C 15 H 11 NO 2 o1575 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 N-Benzylindole-2,3-dione (N-benzylisatin) Mehmet Akkurt, a * Sevim Tu ¨rktekin, a Ali Asghar Jarrahpour, b Dariush Khalili b and Orhan Bu ¨yu ¨kgu ¨ngo ¨r c a Department of Physics, Faculty of Arts and Sciences, Erciyes University, 38039 Kayseri, Turkey, b Department of Chemistry, College of Sciences, Shiraz University, 71454 Shiraz, Iran, and c Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139 Samsun, Turkey Correspondence e-mail: akkurt@erciyes.edu.tr Key indicators Single-crystal X-ray study T = 296 K Mean (C–C) = 0.002 A ˚ R factor = 0.039 wR factor = 0.099 Data-to-parameter ratio = 13.9 For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. Received 20 March 2006 Accepted 21 March 2006. # 2006 International Union of Crystallography All rights reserved The title molecule, C 15 H 11 NO 2 , is non-planar, the dihedral angle between the isatin group and the phenyl ring being 87.08 (5)  . The crystal structure is stabilized by C–HO hydrogen bonding interactions. Comment Isatin is an endogenous indole present in mammalian tissues and fluids (Igosheva et al., 2004). It has a distinct and discontinuous distribution in rat brain and other tissues; highest concentrations in the brain have been found in the hippocampus (about 0.1 mg/ml) and cerebellum (Watkins et al. , 1990). Isatin has shown a wide variety of biological activity on the central nervous system (Glover et al., 1988), such as anticonvulsant (Bhattacharya & Chakraborti, 1998; Bhatta- charya, 1988), anxiogenic (Palit et al., 1997; Medvedev et al. , 1992) and antiviral activity (Webber et al., 1996; Chen et al., 2005). Thus, isatin is a biologically validated starting point for the design and synthesis of chemical libraries directed at these targets. N-Alkylated isatins have interesting pharmacological activities such as antibacterial, antiviral (Garden et al., 1998; Bauer & Sadler, 1960; Skiles & McNeil, 1990) and anticancer (Chazeau et al., 1992) and are reversible and competitive inhibitors of monoamine oxidase A and B (Medvedev et al. , 1995). Mach and his coworkers (Chu et al., 2005) have reported that N-benzylisatin sulfonamide analogues have potent caspase-3 inhibitor activity. Recently, it has been found that certain isatin compounds are potent inhibitors against rhinovirus 3C protease (Webber et al., 1996). The isatin scaf- fold with derivatization may provide a good candidate for the SARS CoV 3CLpro inhibitor because both of the proteases (human SARS CoV and rhinovirus) are cysteine protease and structurally similar at the active site (Chen et al., 2005). The molecular structure of (I) is shown in Fig. 1. The values of the geometric parameters of (I) are within normal ranges, within experimental error. The isatin group in (I) is almost