Dicyclohexylcarbodiimide → N,N'-Dicyclohexylurea

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Reaction Steps

In 50 ml of ethyl acetate was dissolved with heating 1.0 g (2.73 mmole) of the compound obtained in step 1 of Example 1 above. To the resultant solution were added 0.68 g (4.10 mmole) of (-)-α-methoxyphenylacetic acid and then 0.67 g (3.28 mmole) of 1,3-dicyclohexyl carbodiimide at room temperature. Subsequently, 0.040 g (0.33 mmole) of 4-dimethylaminopyridine as a catalyst was added. The resultant mixture was stirred for 24 hours. Dicyclohexyl urea in the form of a white solid produced during the reaction as a side-product was removed by filtration, and the remaining filtrate was concentrated and purified by silica gel column chromatography using a mixture of hexane and ethyl acetate (1:1) as an eluent to obtain 0.70 g (1.36 mmole, yield 50%) of (+) dimethoxymethyl-3-(O-α-methoxy-α-phenylacethoxy)-4-(2'-oxo-1'-pyrrolidinyl)-6-cyano-3,4-dihydro-2H-1-benzopyran having Rf value of 0.23 and 0.54 g (1.05 mmole, yield 38%) of (-) dimethoxymethyl-3-(O-α-methoxy-α-phenylacethoxy)-4-(2'-oxo-1'-pyrrolidinyl)-6-cyano-3,4-dihydro-2H-1-benzopyran having Rf value of 0.30.

Provenance & Evidence