Indole, 12. Mitt. β-Carboline aus Lactonen - Zur Synthese von Liganden am Norharman-Rezeptor

Indoles, XII: β-Carbolines from Lactones - Synthesis of Ligands of the Norharmane Receptor Starting from α-ethoxalyl-δ-valerolactone ( 1 ) 6-substituted β-carbolines were synthesized in 5 steps to enable investigations at the norharmane binding sites in rat liver and in pig brain. The Pd-catalyzed aromatization of N-benzyl-tetrahydro-β-carbolines with debenzylation was optimized with 5a→6a and then used for the preparation of other derivatives. Additional hydrogenolyses occur with 5d,h . Bromination of 1a gives 6d which can be transferred to the radioligand ³H-norharmane.