Recently, the first direct method for preparing 2,3-epoxyamides (glycidic amides) was disclosed. Now in this letter, the enantiopure synthesis of both enantiomers of norbalasubramide featuring this synthetic method is reported. To this end, chiral N-allyltryptamine 12 was prepared and transformed into an inseparable mixture of diastereomeric epoxyamides 13a/13b, which were submitted to intramolecular cyclization with Cu(OTf)2 to afford a separable mixture of eight-membered ring lactams 14a and 14b. Finally, after removal of the protective group and the chiral auxiliary an enantiopure synthesis of the title compounds was completed.
Key words
2,3-epoxyamides - glycidic amides - tandem oxidation - sodium chlorite - balasubramide - norbalasubramide