N-Methylbenzylamine → 3-{6-[6-(N-Benzyl-N-methyl-amino)-purin-9-yl]-2,2-dimethyl-tetrahydro-furo[3,4-d][1,3]dioxol-4-ylmethoxy}-isoxazole-5-carboxylic acid methyl ester

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Reaction Steps

To a solution of 3-[6-(6-Chloro-purin-9-yl)-2,2-dimethyl-tetrahydro-furo[3,4-d][1,3]dioxol-4-ylmethoxy]-isoxazole-5-carboxylic acid methyl ester (0.106 g, 0.23 mmol) in tetrahydrofuran (1.2 mL) was added polymer-bound diisopropylethylamine (PS-DIEA; Argonaut Tech., 3.83 mmol/g, 0.190 g, 3 eq), followed by addition of 0.040 mL of N-methyl-N-benzylamine (1.2 eq). The resulting mixture was stirred at room temperature overnight. The PS-DIEA resin was washed three times with dichloromethane and the solution obtained from the washes was concentrated to yield 3-{6-[6-(N-Benzyl-N-methyl-amino)-purin-9-yl]-2,2-dimethyl-tetrahydro-furo[3,4-d][1,3]dioxol-4-ylmethoxy}-isoxazole-5-carboxylic acid methyl ester as yellow oil. This material (0.23 mmol) was dissolved in 1,4-dioxane (1.2 mL) and 0.250 mL of an aqueous 2M lithium hydroxide solution added. The mixture was stirred at room temperature for 4 h. The crude product, isolated after acid workup, was used without further purification in the following step. MW calculated for C25H26N6O7 (MH+): 523. found 523 by LCMS.

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