Total synthesis of the fumiquinazoline alkaloids: Solution-phase studies

Biomimetic total syntheses of glyantrypine, fumiquinazoline F, fumiquinazol ine G, and fiscalin B were achieved in four steps from tryptophan methyl es ter. In the key step, the anthranilamide residue in a linear tripeptide is dehydrated to a benzoxazine by reaction with triphenylphosphine, iodine, an d a tertiary amine. The benzoxazines subsequently undergo rearrangement to the natural products via an amidine intermediate. This dehydrative oxazine to quinazoline route is applicable to a broad range of N-acylanthranilamide s, including sterically hindered cases.