Patent ID: 6180823
Filing Date: 2001-01-30
Classification: C07C,C07D

Abstract:
A process for preparing an enantiomer of cyclohexylphenylglycolic acid of greater than 50% e.e., comprising the sequential steps of:(a) condensing pivaldehyde or diphenylacetaldehyde with a single enantiomer of mandelic acid in the presence of a sulfonic acid catalyst to provide a corresponding 5-phenyl-1,3-dioxolan-4-one;(b) condensing said 5-phenyl-1,3-dioxolan-4-one with cyclohexanone in the presence of a lithium amide below -40.degree. C. to provide a 5-(1-hydroxycyclohexyl)-5-phenyl-1,3-dioxolan-4-one enriched in one diastereomer;(c) exposing said 5-(1-hydroxycyclohexyl)-5-phenyl-1,3-dioxolan-4-one sequentially to thionyl chloride and then pyridine to provide 5-(1-cyclohexenyl)-5-phenyl-1,3-dioxolan-4-one;(d) hydrolyzing said 5-(1-cyclohexenyl)-5-phenyl-1,3-dioxolan-4-one with an aqueous alkali metal hydroxide to provide .alpha.-cyclohexenylphenylglycolic acid; and(e) reducing said .alpha.-cyclohexenylphenylglycolic acid with hydrogen gas in the presence of a noble metal catalyst to provide .alpha.-cyclohexylphenylglycolic acid enriched in a single enantiomer.