2, 3, 5-Substituted pyrrole derivatives are prepared by treatment of 2, 3-dihydrofuran derivatives with trifluoroacetic acid. These in turn are obtained by Michael addition of carbon nucleophiles of the β-dicarbonyl type to N-(4-toluenesulfonyl)-N-(tert-butyloxycarbonyl)- dehydroalanine methyl ester.