β‐Carboline alkaloids 9 [1]. Total synthesis of the β‐carboline alkaloids arenarine A and (±)arenarine B

The first total synthesis of the β‐carboline alkaloids arenarine A (1) and arenarine B (2) is described. Methanolysis of the α‐bromoketone 9 gives 1 in good yield. Alternatively 1 can be obtained from the diazoketone 11 with boron trifluoride/methanol in poor yield. Reduction of 1 with sodium borohydride gives racemic arenarine B (2). Regioselective homolytic methylation of norharmane (4) with tert ‐butyl hydroperoxide/ferrous sulfate gives the alkaloid harmane (6).