Synthesis and stereochemistry of new trihydrodiazabicyclo-[3.m.n]alkano[4′,5′:1,2]pyrido[3,4-b]indole ring system

The classical Pictet‐Spengler reaction of tryptamine with the isomeric N ‐benzylpiperidones 3a, 3b and N ‐benzylpyrrolidone 3c yielded the spiro derivatives of 1,2,3,4‐tetrahydro‐β‐carboline 5a, 5b and 5c . Cyclocon‐densation of the spirotetrahydrocarboline with chloroacetic chloride and the subsequent reductive debenzylation afforded the new ring systems of trihydrodiazabicyclo[3.m.n]alkano[4′,5′:1,2]pyrido[3,4‐ b ]indoles 8a , 8b , and 8c ....