Der Farbstoff aus der Wöhlkprobe: Eine Schutzgruppe in Position 4 der Glucose reicht, damit sich die alkalische Zuckerlösung mit Ammoniak oder Methylamin verfärbt

At the Woehlk test (Copenhagen 1904) and the very similartest by Fearon (Dublin 1942), it was not yet known which substance causes the red color

and which mechanism it produces. In the meantime, UV Vis spectroscopic examinations, in the truest sense of the word, put some light into the matter. The article contains suggestions for the chromophore; the mechanism of formation is similar to that of the early and middle Maillard reaction. In view of the fact that the red dye is formed not only with lactose and maltose, but also with cellobiose, maltotriose and the rearrangement products lactulose and maltulose, it has been hypothesized that a protection group in position 4 of the glucose would be sufficient to produce a successful Woehlk or Fearon test. This could now be confirmed in Kiel with 4,6-O-ethylidene-D-glucopyranose.