Two series of chemically related, conformationally restricted ring systems were synthesized. Bridged tetrahydro-β-carbolines, designed as selective 5-HT receptor ligands, were formed via Pictet–Spengler condensation of cyclic tryptamine precursors. Oxidation of the indole 2- position of the precursors followed by condensation with aldehydes produced spiro-cyclic quinuclidines, containing important muscarine receptor pharmacophores.
