Support studies toward the alkaloids mescengricin and lysiformine focused on oxazole-olefin cycloadditions

Abstract

An oxazolo[4,5-b]indole serves as an azadiene in a regioselective Kondrat'eva reaction forming the core of the neuroprotective alkaloid mescengricin, the first such application of this venerable [4 + 2]-cycloaddition for the synthesis of α-carbolines. In a reaction that has possible biosynthesis implications, the 6-(indolylmethyl)pyridin-3-ol unit of the marine-derived alkaloid lysiformine has also been prepared by a regioselective Kondrat'eva reaction using a 2-(indolylmethyl)-5-ethoxyoxazole as the azadiene.