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

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