A Suzuki‐Miyaura Coupling of Ortho Hydroxy Aryl Bromide with Isopropenylboronic Pinacol Ester and its Application: Synthesis of the Potassium‐Channel Opener (+)‐Callitrisic Acid
Xiongyu Wu; Malin Silverå Ejneby; Nina Ottosson; Fredrik Elinder; Peter Konradsson
A Suzuki‐Miyaura coupling reaction of ortho hydroxy aromatic bromide 2 with isopropenylboronic acid pinacol ester has been investigated. It was found that the catalyst of Pd2(dba)3/PCy3 in dioxan‐water gave good yield by suppressing the isomerization of isopropen. (+)‐Callitrisic acid was synthesized from (+)‐podocarpic acid using this condition with an overall yield of 54% in about five steps. (+)‐Callitrisic acid was found to be almost three times more potent than dehydroabietic acid to open a voltage‐gated potassium channel.