Method for producing pyrrolidine derivative

A method for producing a compound represented by formula (l):

• (wherein R2 represents a lower alkyl group, and R4 represents an alkyl group which may be substituted or an aralkyl group which may be substituted), comprising:
• reducing a compound represented by formula (h):
• (wherein R5 represents a hydrogen atom or a protecting group for the amino group) to thereby produce a compound represented by formula (i):
• treating the compound represented by formula (i) with a base in an aprotic polar solvent and then reacting with water to thereby produce a compound represented by formula (j):
• and either
• (A) treating the compound represented by formula (j) with an acid in the presence of an alcohol to thereby produce a compound represented by formula (k):
• and treating the compound represented by formula (k) with camphorsulfonic acid to thereby isolate an isomer as an acid adduct salt, or
• (B) treating the compound represented by formula (j) with camphorsulfonic acid to thereby isolate an isomer as an acid adduct salt, or
• (C) isolating the compound represented by formula (j) as a salt and then treating the salt with an acid in the presence of an alcohol to thereby produce a compound represented by formula (k);
• and treating the compound represented by formula (k) with camphorsulfonic acid to thereby isolate an isomer as an acid adduct salt, or
• (D) isolating the compound represented by formula (j) as a salt and then treating the compound with camphorsulfonic acid to thereby isolate an isomer as an acid adduct salt.