Zheng Bao-hui
2008
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Journal
Fine chemicals
Abstract
Firstly,protection of 6-hydroxyl of D-glucono-1,5-lactone was achieved by trityl chloride(TrCl) in pyridine at room temperature.Then hydrolysis of 6-O-Tr-D-glucono-1,5-lactone in 30% KOH methanol solution was conducted.To a solution of resulting gluconate in DMSO,NaH(12eq.) and EtBr(11eq.) were added at 0 ℃,and the solution was stirred for 3 h at 25 ℃.Ethyl 6-O-Tr-2,3,4,5-O-tetraethylgluconate(Ⅳa) was obtained with a total yield of 40% in 3 steps.Secondly,compound Ⅳa was heated in aqueous acetic acid(VHOAc/VH2O=4) at 70 ℃ for 2 h to give ethyl tetraethylgluconate(Ⅴ).Tetraethylgluconic acid(Ⅵ) was prepared from hydrolysis of compound Ⅴ in KOH solution then acidified by 5% HCl.At the end,dehydration of compound Ⅵ by dicyclohexylcarbodiimide(DCC),4-dimethylaminopyridine(4-DMAP) and 4-dimethylaminopyridine hydrochloride(4-DMAP·HCl) gave the target compound tetraethylglucono-1,6-lactone.The synthesis route was optimized.In the process of ethylation,excess NaH(23eq.) was added,and MeOH and water were dropped when the reaction was completed.Ester bond of compound Ⅳa was destroyed in alkaline solution to produce 6-O-Tr-2,3,4,5-O-tetraethylgluconic acid(Ⅳb).Deprotection of 6-OH of compound Ⅳb furnished compound Ⅵ.Hence,a one-pot reaction containing protection of hydroxyl and deprotection of carboxyl was developed,and the purification process was also simplified.The structure of target compound was confirmed by 1HNMR.