Noncompetitive NMDA antagonists: a novel synthesis of 1-phenyltetrahydro-3-benzazepines

The key step in the synthesis of the pharmacologically interesting 1-phenyltetrahydro-3-benzazepine skeleton is the Michael addition of (2-lithiophenyl)acetaldehyde acetals, which are generated in situ upon treatment of the bromo acetals 5a,b with n-butyllithium, to beta-nitrostyrene (6). The reductive ring closure of the nitro acetals 7a,b succeeded with zinc dust and hydrochloric acid to give the 3-benzazepines 11a,b in good yields. The unsubstituted 3-benzazepine 11a showed a considerable affinity for the phencyclidine binding site of the NMDA receptor (Ki = 6.41 microM), whereas donor substituents in the aryl moiety (11b,c) reduce the affinity for the NMDA receptor.