Synthesis of C‐14‐labeled novel IKK inhibitor: 2‐[ 14 C]‐ N ‐(6‐chloro‐9H‐pyrido [3,4‐b]indol‐8‐yl)‐3‐pyridinecarboxamide

2‐[ 14 C]‐ N ‐(6‐Chloro‐9H‐pyrido [3,4‐b]indol‐8‐yl)‐3‐pyridinecarboxamide ( 9A , also referred to as [ 14 C]‐PS‐1145) was synthesized from [ 14 C]‐paraformaldehyde in five steps in an overall radiochemical yield of 15%. The key intermediate 1‐[ 14 C]‐6‐chloro‐1,2,3,4‐tetrahydro‐ β ‐carboline was obtained by Pictet–Spengler cyclization of chlorotryptamine with [ 14 C]‐paraformaldehyde. Similar reactions were conducted with tryptamine to address the generality of the methodology. Copyright © 2005 John Wiley & Sons, Ltd.