Synthesis of 1,4-dihydropyridinyl glucosamine derivative as water soluble fluorescent sensor

Abstract

Glucosamine (GlcNH) is an amino sugar synthesizable from chitin and chitosan of two marine crustaceans: shrimp and crab, abundant resource in Thailand. The new way to utilize GlcNH has to be developed; otherwise this resource will be wasted more than 500,000 tons a year. 1,4-Dihydropyridinyl Glucosamine (Glc-DHP 1) has been synthesized as a new fluorescent sensor. Primary amine was obtained from D-glucosamine hydrochloride (GlcNHCl) as the starting material by using the reported synthetic procedure [55]. Subsequent addition reaction of the primary amine and ethyl propiolate in CH2Cl2 under refluxing temperature for 3 days was carried out to produce β-amino acrylate. The cyclotrimerization (3 eq.) of the β-amino acrylate to Glc-DHP 1 was observed smoothly in the presence of TiCl4. This DHP derivative is soluble in aqueous media and the solution gives blue fluorescent signal with quantum yield of 0.29. By possessing fluorescence property, this Glc-DHP 1 was used as fluorescent chemosensor for the detection of explosive compounds. The fluorescence signal of Glc-DHP 1 was selectively quenched by 2,4,6-trinitrophenol without the interference of other nitroaromatics with high quenching efficiency (Ksv = 44,700 M-1) and a detection limit of 0.94 µM. Also the detection could be observed by naked eye under black light. Moreover, Glc-DHP 1 was also tested as fluorescent biosensor for the detection of protiens; e.g. BSA, hemoglobin, papain, etc. The fluorescence signal of Glc-DHP 1 was selectively quenched by hemoglobin, cytochrome c and myoglobin with Ksv = 424,000 M-1, 53,400 M-1 and 52,200 M-1, respectively.