Abstract: A process for producing a high purity 3,5-dihydroxy6-heptenoic acid derivative by controlling the content of impurities such as denatured substances, is provided. When a 3,5-dihydroxy-6-heptenoic acid derivative is produced by a process which comprises a step of contacting the 3,5-dihydroxy-6-heptenoic acid derivative of the formula (1) wherein R is a C1-4 alkyl group, with a C1-4 lower alcohol-containing solvent, an alcohol containing solvent having its content of an oxidizing substance lowered, is used to at most 0.05 molar equivalent to a 3,5-dihydroxy-6-heptenoic acid derivative, to suppress impurities contained in the 3,5-dihydroxy-6heptenoic acid derivative.

Abstract: A method for producing an alkyl (3R,5S)-7-[2-cyclopropyl-4-(4-fluorophenyl)quinolin-3-yl]-3,5-dihydroxy-6-heptenoate of the formula (1) (wherein R is a C1-4 alkyl group), which is an intermediate for a cholesterol-reducing agent (a HMG-CoA reductase inhibitor), etc. A solution containing a compound of the formula (1) is subjected to liquid chromatography treatment using silica gel as the packing material, to separate its epimers contained therein.

Abstract: A process for producing a high purity 3,5-dihydroxy6-heptenoic acid derivative by controlling the content of impurities such as denatured substances, is provided. When a 3,5-dihydroxy-6-heptenoic acid derivative is produced by a process which comprises a step of contacting the 3,5-dihydroxy-6-heptenoic acid derivative of the formula (1) wherein R is a C1-4 alkyl group, with a C1-4 lower alcohol-containing solvent, an alcohol containing solvent having its content of an oxidizing substance lowered, is used to at most 0.05 molar equivalent to a 3,5-dihydroxy-6-heptenoic acid derivative, to suppress impurities contained in the 3,5-dihydroxy-6heptenoic acid derivative.

Abstract: A method for producing an alkyl (3R,5S)-7-[2-cyclopropyl-4-(4-fluorophenyl)quinolin-3-yl]-3,5-dihydroxy-6-heptenoate of the formula (1) (wherein R is a C1-4 alkyl group), which is an intermediate for a cholesterol-reducing agent (a HMG-CoA reductase inhibitor), etc. A solution containing a compound of the formula (1) is subjected to liquid chromatography treatment using silica gel as the packing material, to separate its epimers contained therein.

Abstract: A method for producing ? crystals of ethyl (R)-2-[4-(6-chloro-2-quinoxalin-2-yloxy)phenoxy]propionate, which is characterized by heating ? crystals, or ? crystals and ? crystals, within a range of from 50° C. to lower than the melting point of the ? crystals.

Abstract: A method for producing high melting point crystals, which is characterized by heating ethyl=(R)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate in the form of low melting point crystals, or low melting point crystals and high melting point crystals, within a range of from 50° C. to lower than the melting point of the low melting point crystals.

Abstract: A method for producing &bgr; crystals of ethyl (R)-2-[4-(6-chloro-2-quinoxalin-2-yloxy)phenoxy]propionate, which is characterized by heating &agr; crystals, or &agr; a crystals and &bgr; crystals, within a range of from 50° C. to lower than the melting point of the &agr; crystals.