Reaction of alcohols and amines with diacetyldihydrofluorescein (DADF): Conversion into erythrosine-derivatives on TLC-plates by ammonia and iodine vapors
✍ Scribed by Paam N. Sharma; Arnold Brossi
- Book ID
- 102253170
- Publisher
- John Wiley and Sons
- Year
- 1984
- Tongue
- German
- Weight
- 276 KB
- Volume
- 67
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Reaction of deacetylcolchicine (2) and colchifoline (3) with diacetyldihydrofluorescein (1, DADF) afforded the corresponding amide and ester derivatives, converted on TLC-plates after exposure to ammonia and iodine vapors into red colored pigments. This reaction, also observed with DADF-derivatives of codeine, quinine and mescaline is highly sensitive. The red pigment produced from the DADF-ester (6) of colchifoline formed by the ammonia-iodine treatment is the corresponding erythrosine ester derivative. DADF emerges from these investigations as a useful reagent to detect alcohols and amines in crude mixtures and for dye labeling.
Diacetyldihydrofluorescein (1, DADF) is a well known compound [ 11, and easily available from fluorescein by reduction with Zn/NH,Cl in refluxing EtOH, followed by acetylation of the dihydrocompound with Ac,O in pyridine. A TLC analysis of DADF afforded red colored spots after exposure of the material on plates to ammonia and iodine vapors suggesting that a similar color reaction might also occur with derivatives of DADF. In search for high affinity probes to map the colchicine binding site on tubulin 121 [3], we considered it worthwhile to prepare DADF-derivatives of the biologically potent colchinoids, deacetylcolchicine (2) and colchifoline (3) [3], hoping that they would bind to tubulin protein and could then be made visible in free and bound form by the color reaction. Reaction of 2 and 3 with DADF in dry CH,Cl, in the presence of dicyclohexylcarbodiimide and a catalytic amount of 4-dimethylaminopyridine [4] afforded the crystalline amide 5 and the ester 6, respectively. Treatment of the amide 5 with aqueous ammonia afforded the diphenol7, further converted with H,O, in ethanol into a yellow-green fluorescent dye with properties similar to fluorescein. Although 5 and 6 did not bind to tubulin protein sufficiently (15 and 30%, respectively) [5], after chromatography and exposure of the plates to ammonia and iodine vapors they both developed red colors similar to those already observed with DADF. The crude dyes obtained from 5 and 6 after extraction from the silica gel TLC plates contained large amounts of iodine and showed UV maxima at 546 nm in EtOH, suggesting that the reactions on plates possibly involved conversion of the DADF-part