INDOLES .12. BETA-CARBOLINES FROM LACTONES - SYNTHESIS OF LIGANDS OF THE NORHARMANE RECEPTOR

Starting from alpha-ethoxalyl-delta-valerolactone (1) 6-substituted beta-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-beta-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 H-3-norharmane.