Methanol → Ethyl 6-((tert-butoxycarbonyl)methyl)-2,2-dimethyl-1,3-dioxane-4-carboxylate

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Reaction Steps

To a solution of 1-ethyl 6-tert.-butyl 2,4-dihydroxyadipate (1.6 g, 6.1 mmol) in methylene chloride (60 ml), dimethoxypropane (1.672 ml, 78 mmol) and pyridinium p-toluenesulfonate (251 mg, 1 mmol) were added and stirred under reflux conditions for one hour, followed by further stirring at 50° C for one hour while azeotropically removing methanol with methylene chloride. To the mixture, methylene chloride (60 ml) was added and stirred at 50° C. for one hour to remove methylene chloride. After adding water, the mixture was extracted with methylene chloride. The organic layers were combined, dried over sodium sulfate and concentrated under reduced pressure. The residue was subjected to silica gel column chromatography (hexane:acetone=7:1) to give pure 2-ethoxycarbonyl-4-tert.-butoxycarbonylmethyl-6,6-dimethyl-1,5-dioxane (1.23 g, 4.06 mmol). Yield, 67%.

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