Synthesis of Poly(3,4,5-trihydroxybenzoate) dendrimers from Polyphenols and Their Chemiluminescence

Abstract

Dendrimer chemistry is rapidly expanding both for fundamental reasons as well as due to requirements in technological applications.1 A recent interesting development in dendrimer chemistry concerns the coordination of metal ions by interior branches or exterior units. [2][3][4][5][6] Dendrimers containing photoactive units [7][8][9][10][11][12][13][14][15][16][17] are particularly interesting for two reasons: (1) cooperation among the photoactive components can allow the dendrimer to perform specific functions, and (2) changes in the properties of photoactive components can be exploited to monitor the participation of dendrimers in chemical processes.Polyphenols such as pyrogallol and gallic acid (GA) produce a singlet oxygen in the presence of hydrogen peroxide in an alkaline medium and emit light. GA has also been utilized for selective Co 2+ detection using a chemiluminescence (CL) flow injection system. The CL intensities of polyphenols are considerably weaker than those of luminal and acridinium ester, which are representative CL compounds. Hence, trans-4-(3-propionic acid)phenylboronic acid and 4-biphenylboronic acid in the presence of peroxidase or 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide have been used as an enhancer for highly sensitive polyphenol CL determination. However, methods to derive polyphenols with strong CL intensity have not been reported yet. 18In recent times, after a new polymer, poly(amidoamine) dendrimer, was synthesized, dendrimers have been applied to material engineering based on optics in nanoscale science. The poly(propylene amine) family that was functionalized in the periphery with fluorescent dansyl units interacts with Co 2+ . More recently, acridinium dendrimers have been conjugated with bovine serum albumin, and its CL was estimated to be six times that of the acridinium salt.In this paper, we report the design of new types of polyphenol dendrimers having an increased number of chemiluminophores for high CL intensity; they also have hydroxyl groups in their periphery to form hydrogen bonds with an analyst. Polyphenol dendrimers having GA in the periphery were synthesized, and their CL was measured. We synthesized first-generation polyphenol dendrimers with GA units in the periphery by employing a divergent method using phenol, pyrocatechol, resorcinol, hydroquinone, 1,2,4-trihydroxybenzene, and 3,4,5-trihydroxybenzene as the core molecules (Schemes 1-3).The esterification of 3,4,5-trihydroxybenzoyl chloride with phenol yielded 2a in 80%. After the debenzylation of 2a, we were able to separate 3a and the byproduct by chromatographic purification. Therefore, the desired zero-generation ester 3a was not isolated. Compounds 4a and 5a were synthesized by repeating this esterification and debenzylation, respectively, but the yield of the first-generation ester 5a was 91%. The esterification of 3,4,5-trihydroxybenzoyl chloride with pyrocatechol, 3,4,5-trihydroxybenzoyl chloride with resorcinol, and 3,4,5-trihydroxybenzoyl chloride with hydroquinone yielded 2b (95%), 2c (96%), a...

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