Complete 1H NMR assignment of 3-formylindole derivatives

-Formylindoles including indolylglyoxylate esters andindolylglyoxylamides are widely found in nature as alkaloids,[1]andare important building blocks or synthetic intermediates for drugdiscovery,[2]and for the synthesis of natural products.[3]Acarefulin-spection of the1H NM R data of these molecules[4]reveals that multi-plicities for H4 and H7 are reported as broad doublets,[4a,4b]asdoublet of doublets-like,[4b]as a combination of doublet of doubletsand multiplets,[4a,4b]or simply as doublets.[4c,4d]InthecaseofH5andH6, they are reported as triplet of doublets,[4a,4b]as triplets,[4c]or as dou -blet of triplets[4d]despite the fact that in most cases, their chemicalshifts are claimed to be unambiguously assigned. In addition, incorrectcoupling constant values for the incorrect multiplicities for H4?H7 arealso reported. A prudent signal description of the H4?H7 system israrely given as multiples without reporting coupling constant values.[4e