Crystal structures of four indole derivatives as possible cannabinoid allosteric antagonists

The crystal structures of four indole derivatives with various substituents at the 2-, 3- and 5-positions of the ring system are described, namely, ethyl 3-(5-chloro-2-phenyl-1H-indol-3-yl)-3-phenyl­propano­ate, C(25)H(22)ClNO(2), (I), 2-bromo-3-(2-nitro-1-phenyl­eth­yl)-1H-indole, C(16)H(13)BrN(2)O(2), (II), 5-meth­oxy-3-(2-nitro-1-phenyl­eth­yl)-2-phenyl-1H-indole, C(23)H(20)N(2)O(3), (III), and 5-chloro-3-(2-nitro-1-phenyl­eth­yl)-2-phenyl-1H-indole, C(22)H(17)ClN(2)O(2), (IV). The dominant inter­molecular inter­action in each case is an N—H⋯O hydrogen bond, which generates either chains or inversion dimers. Weak C—H⋯O, C—H⋯π and π–π inter­actions occur in these structures but there is no consistent pattern amongst them. Two of these compounds act as modest enhancers of CB1 cannabanoid signalling and two are inactive.