Practical Syntheses of Functionalized 1-Oxo-L,2,3,4-Tetrahydro-β-carboline-3-carboxylic Acid Esters

Abstract Three methods have been proposed for the preparation of functionalized 1-oxo-1,2,3,4-tetrahydro-β-carboline-3 carboxylates (3) from which the “acylazide formation-Curtius rearrangement-acid catalyzed ring closure” sequence starling from hemi-ester hemi-acids (8) seemed to be quite general.