Hydrochloric Acid → (4R)-2,2-Dimethyl-1,3-dioxolane-4-carboxylic acid

Beteiligte Stoffe

Reaktionsschritte

To a 2 N aqueous solution of potassium hydroxide was added (R)-(+)-2,2-dimethyl-1,3-dioxolan-4-carboxylic acid methyl ester (1.00 g, 6.24 mmol), followed by stirring under ice cooling conditions for 3 hours. After neutralization with hydrochloric acid, the solution was salted out and extracted with ethyl acetate (50 ml) to yield (R)-(+)-2,2-dimethyl-1,3-dioxolan-4-carboxylic acid as colorless amorphous powders (0.72 g). To a solution of the compound obtained in Reference Example 29 (0.572 g, 1.0 mmol) in dichloromethane (5 ml) were added diisopropylethylamine (1.04 g, 8 mmol) and the (R)-(+)-2,2-dimethyl-1,3-dioxo-lane-4-carboxylic acid obtained (0.292 g, 2 mmol), followed by stirring under ice cooling conditions. To this solution was added benzotriazol-1-yloxytrisdimethylaminophosphonium hexafluorophosphate (BOP reagent) (0.885 g, 2 mmol). After stirring under ice cooling conditions for 1 hour, the solution was further stirred at room temperature for 4 days. The reaction mixture was concentrated to dryness under reduced pressure, and then the obtained residue was partitioned between water (50 ml) and chloroform (50 ml). The water layer was again extracted with chloroform (10 ml). The combined extracts were washed with saline, and dried (MgSO4), the solvent was distilled off under reduced pressure. The obtained residue was chromatographed on silica gel to yield colorless amorphous powders (0.5 g),which was then dissolved in trifluoroacetic acid (10 ml) and stirred at room temperature for 16 hours. The reaction mixture was concentrated to dryness under reduced pressure and treated with alkali, after which it was partitioned between chloroform (50 ml) and water (50 ml), and then the water layer was again extracted with chloroform (10 ml). The combined extracts were washed with saline, and dried (MgSO4), the solvent was distilled off under reduced pressure. The obtained residue was chromatographed on silica gel to yield 0.5 g of colorless amorphous powders (76%).

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