Model studies related to the total synthesis of the fumitremorgins; the Pictet-Spengler cyclisation and the formation and intramolecular acylation of a 1,2-dihydro-β-carboline derivative

Article abstract of DOI:10.1016/S0040-4020(01)89899-9

The preparations of the tetrahydro-β-carbolines 8, 9b, and 9d are described. The Pictet-Spengler reaction of L-tryptophyl-L-proline methyl ester with 3-methylbutanal gave the tetrahydro-β-carbolines 20 and 21; subsequent acid-catalysed cyclisation afforded the fumitremorgin analogues 22 and 23. The 2-(p-toluenesulphonyl)tetrahydro-β-carboline 27a furnished the unsaturated pentacycle 28a upon treatment with alkali.