experiments. Studies on their formation revealed that 1a, b and 2a, b are formed upon condensation of pentose-derived 4-hydroxy-5-methyl- (3) and 5-methyl-4-(pyrrolidin-1-yl)furan-3(2H)-one (4), respectively, with 2-hydroxycyclopenta-2,4-dien-1-one (5) and L-proline (Scheme 1). Further condensation reaction of 1a, b with furan-2-carbaldehyde yielded the red (2Z)-2-(5Z)-5-[(2-furyl)methylidene]-4-oxo-3-(