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-phenyl-propano-ate, C25H22ClNO2, (I), 2-bromo-3-(2-nitro-1-phenyl-eth-yl)-1H-indole, C16H13BrN2O2, (II), 5-meth-oxy-3-(2-nitro-1-phenyl-eth-yl)-2-phenyl-1H-indole, C23H20N2O3, (III), and 5-chloro-3-(2-nitro-1-phenyl-eth-yl)-2-phenyl-1H-indole, C22H17ClN2O2, (IV). The dominant inter-molecular inter-action 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 inter-actions 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.