New approaches to the synthesis of canthin-4-one alkaloids and synthetic analogues

作者：Tremmel Tim; Bracher Franz^*

来源：Tetrahedron, 2015, 71(28): 4640-4646.

DOI：10.1016/j.tet.2015.05.002

• Alkaloids
• Canthin-4-ones
• beta-Carbolines
• Isoxazoles
• Cyclization
• Enaminoketones

Two novel approaches to the canthin-4-one ring system have been worked out Claisen-type condensation of 1-acetyl-beta-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-beta-carboline and 1-isoxazolyl-beta-carbolines, followed by reductive isoxazole cleavage and cyclization, is more versatile. 5,6-disubstituted canthin-4-ones are accessible via iodination at C-5 and subsequent Pd-catalyzed cross-coupling.

• 出版日期2015-7-8