New approaches to the synthesis of canthin-4-one alkaloids and synthetic analogues
作者:Tim Tremmel、Franz Bracher
DOI:10.1016/j.tet.2015.05.002
日期:2015.7
Two novel approaches to the canthin-4-one ring system have been worked out. Claisen-type condensation of 1-acetyl-β-carboline with N-acyl benzotriazoles gives, via intermediate 1,3-diketones, 6-alkylcanthin-4-ones in one single operation, but this protocol is restricted to small alkyl substituents. An alternative approach, via 1-ethynyl-β-carboline and 1-isoxazolyl-β-carbolines, followed by reductive