Preparation of stereoisomers of ketals
AssigneeSyntex (U.S.A.) Inc.
InventorGeorge C. Schloemer
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Abstract
Pharmaceutically useful optically active .alpha.-arylalkanoic acids or esters, ortho esters, or amides thereof are stereoselectively prepared by contacting an aryl magnesium Grignard reagent with an optically active .alpha.-substituted acyl halide to form the optically active aryl .alpha.-substituted alkyl ketone, which is ketalized and rearranged to the desired optically active .alpha.-arylalkanoic acid or the corresponding ester, ortho ester or amide. In an alternate embodiment, the aryl .alpha.-substituted alkyl ketone is reduced to the corresponding alkanol, which is rearranged to the .alpha.-arylalkanal. The alkanal so produced is converted to the desired optically active .alpha.-arylalkanoic acid by conventional methods.
Claims14
A process for producing a single stereoisomer of a ketal of a compound of the formula:
- ##STR48## in the substantial absence of any other stereoisomer of said ketal, said single stereoisomer of said ketal having a preselected absolute configuration, which comprises contacting a stereoisomer of said compound having said preselected absolute configuration in the substantial absence of any other stereoisomer of said compound with a ketalizing agent effective to maintain said preselected absolute configuration selected from the group consisting of ortho esters and polyhydric alcohols, wherein Ar is substituted or unsubstituted naphthyl, R.sub.1 is alkyl or cycloalkyl and Z is halogen, hydroxy, protected hydroxy or a sulfonyloxy group of the formula ##STR49## wherein R.sub.2 is alkyl, cycloalkyl, alkenyl, alkynyl, aryl or arylalkyl.
A process for producing a first compound consisting essentially of a single stereoisomer of a ketal of a second compound of the formula:
- ##STR50## said single stereoisomer of said ketal having a preselected absolute configuration, which comprises contacting said second compound consisting essentially of a single stereoisomer of said second compound having said preselected absolute configuration with a ketalizing agent effective to maintain said preselected absolute configuration selected from the group consisting of ortho esters and polyhydric alcohols, wherein Ar is substituted or unsubstituted naphythyl, R.sub.1 is alkyl or cycloalkyl and Z is a halogen, hydroxy, protected hydroxy or a sulfonyloxy group of the formula ##STR51## wherein R.sub.2 is alkyl, cycloalkyl, alkenyl, alkynyl, aryl or arylalkyl.
Dependencies are inferred from the claim text.