The reactivity of the 1, 2, 3, 4-tetrahydrocarbazol-4-one derivatives has been analysed and applied to the synthesis of (±)-18-noraspidospermidine (1b). This was synthesised, starting from 4-(1′, 3′-dioxolan-2′-yl) cyclohexanone which was successively transformed to 3- methyl-3-(3′-nitropropyl)-1, 2, 3, 4-tetrahydrocarbazol-4-one and to the imine tetracycle 13 by means of nickel boride catalyst. The reduction of 13 to the natural cis D ring junction ...