Dimethoxymethane → 1-(4-Chlorobenzyl)-3-methoxymethoxymethyl-3-methyl-2-oxocyclopentane carboxylic acid methyl ester

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Reaction Steps

1-(4-Chlorobenzyl)-3-methyl-3-hydroxymethyl-2-oxocyclopentane carboxylic acid methyl ester (Compound (XI), R1=CH3, R2=CH3, Ym=4-Cl) (186 mg, 0.60 mmol) was dissolved in methylene chloride (5.6 ml), and dimethoxymethane (2.8 ml) was added. This was cooled in a water bath, diphosphorus pentoxide (372 mg) was added and vigorous stirring was conducted at room temperature for 10 minutes. After completion of the reaction, saturated brine was combined with the reaction solution, and extraction with diethyl ether was conducted. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate. The solvent was distilled away and dried under reduced pressure to obtain a crude 1-(4-chlorobenzyl)-3-methoxymethoxymethyl-3-methyl-2-oxocyclopentane carboxylic acid methyl ester (Compound (X), R1=CH3, R2=CH3, Ym=4-Cl, G=CH2OCH2OCH3) (195 mg). From this, an aliquot (188.8 mg) was dissolved in isopropanol (0.53 ml), a 2M aqueous solution of sodium hydroxide (0.53 ml, 1.12 mmol) was added, and stirring was conducted at 60 degrees C. for 1 hour. After completion of the reaction, water was added and extraction with ethyl acetate was conducted. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate. The solvent was distilled away, and the residue was purified by silica gel column chromatography (eluent; hexane:ethyl acetate=7:1) to obtain the desired substance as a mixture of two isomers (Isomer (a):Isomer (b)=36:65).

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