A practical conversion method of carbohydrates into N-substituted 5-(hydroxymethyl)pyrrole-2-carbaldehydes (pyrralines) was developed by the reaction with primary amines and oxalic acid in DMSO at 90 °C. Further cyclization of the highly functionalized pyrralines afforded the pyrrole-fused poly-heterocyclic compounds as potential intermediates for drugs, food flavors, and functional materials. The mild Maillard variant of carbohydrates and amino esters in heated DMSO with oxalic acid expeditiously produced the pyrrole-2-carbaldehyde skeleton, which can be concisely transformed into the pyrrole alkaloid natural products, 2-benzyl- and 2-methylpyrrolo[1,4]oxazin-3-ones 8 and 9, lobechine 10, and (-)-hanishin 11 in 23-32% overall yields from each carbohydrate.

Homogenous bis-sulfonic acid ionic liquids (1 mol equiv.) in DMSO (10 mol equiv.) at 100 °C efficiently mediated the conversion of D-fructose into 5-hydroxymethyl-2-furfural in 75% isolated yield, which was roughly a 10% increment compared to the case of the mono-sulfonic acid ionic liquids.

One-Pot Conversion of Carbohydrates into Pyrrole-2-carbaldehydes as Sustainable Platform Chemicals. -Carbohydrates such as glucose (I) are converted into title compounds (III) by the reaction with primary amines (II) in the presence of oxalic acid. Further cyclization of these compounds affords fused poly-heterocyclic systems. The products of the mild Maillard reaction of carbohydrates and amino esters can be further transformed into natural pyrrole alkaloids, such as lobechine and hanishin. -(ADHIKARY, N. D.; KWON, S.; CHUNG, W.-J.; KOO*, S.; J. Org. Chem. 80 (2015) 15, 7693-7701, http://dx.doi.org/10.1021/acs.joc.5b01349 ; Dep. Energy Sci. Technol., Myongji Univ., Yongin, Gyeonggi 449-728, S. Korea; Eng.) -M. Paetzel 51-116