A method of producing an optically active form of a compound represented by the following formula: wherein R 1 is a C 1-6 alkyl group; R 2 is a hydrogen atom or a halogen atom; R 3 is a hydrogen atom or an optionally halogenated C 1-6 alkyl group; PG is a protecting group; and the carbon atom marked with * is an asymmetric carbon atom, or a salt thereof, which comprises subjecting a compound represented by the following formula: wherein each symbol is as defined above, or a salt thereof, to an asymmetric reduction reaction, wherein the asymmetric reduction reaction is a reduction reaction in the presence of an iridium complex and a reducing agent, wherein the iridium complex is [IrCl] 2, [IrBr] 2, [IrI] 2, [IrCp*] 2, [Ir (cod)]OTf, [Ir (cod)]BF 4, [Ir(cod)]ClO 4,[Ir(cod)]PF 6,[Ir(cod)]SbF 6, [Ir(cod)]BPh 4, [Ir (cyclooctadiene)]B{3,5-(CF 3) 2 C 6 H 3) 4, [Ir(nbd)]OTf, [Ir(nbd)]BF 4, [Ir (nbd)]ClO 4, [Ir(nbd)]PF 6, [Ir(nbd)]SbF 6, [Ir (nbd)]BPh 4, [Ir (nbd)]B{3,5-(CF 3) 2 C 6 H 3} 4, or [Ir(n-allyl) ((C,O)-substituted-benzoate)], wherein L is a ligand selected from: (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)dimethylamine (MonoPhos); (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)benzyl(methyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4-yl)-(1-phenylethyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)bis(1-phenylethyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4-yl)-2,5-diphenylpyrrolidine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)morpholine (Morfphos); and (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)piperidine (PipPhos);and wherein PG is represented by the following formula: wherein Ar 1 is a C 6-14 aryl group optionally substituted by C 1-6 alkoxy; Ar 2 is a C 6-14 aryl group optionally substituted by C 1-6 alkoxy. R 1 is a C 1-6 alkyl group; R 2 is a hydrogen atom or a halogen atom; R 3 is a hydrogen atom or an optionally halogenated C 1-6 alkyl group; PG is a protecting group; and the carbon atom marked with * is an asymmetric carbon atom, or a salt thereof, which comprises subjecting a compound represented by the following formula: wherein each symbol is as defined above, or a salt thereof, to an asymmetric reduction reaction, wherein the asymmetric reduction reaction is a reduction reaction in the presence of an iridium complex and a reducing agent, wherein the iridium complex is [IrCl] 2, [IrBr] 2, [IrI] 2, [IrCp*] 2, [Ir (cod)]OTf, [Ir (cod)]BF 4, [Ir(cod)]ClO 4,[Ir(cod)]PF 6,[Ir(cod)]SbF 6, [Ir(cod)]BPh 4, [Ir (cyclooctadiene)]B{3,5-(CF 3) 2 C 6 H 3) 4, [Ir(nbd)]OTf, [Ir(nbd)]BF 4, [Ir (nbd)]ClO 4, [Ir(nbd)]PF 6, [Ir(nbd)]SbF 6, [Ir (nbd)]BPh 4, [Ir (nbd)]B{3,5-(CF 3) 2 C 6 H 3} 4, or [Ir(n-allyl) ((C,O)-substituted-benzoate)], wherein L is a ligand selected from: (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)dimethylamine (MonoPhos); (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)benzyl(methyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4-yl)-(1-phenylethyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)bis(1-phenylethyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4-yl)-2,5-diphenylpyrrolidine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)morpholine (Morfphos); and (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)piperidine (PipPhos);and wherein the asymmetric reduction reaction is a reduction reaction in the presence of an iridium complex and a reducing agent, wherein the iridium complex is [IrCl] 2, [IrBr] 2, [IrI] 2, [IrCp*] 2, [Ir (cod)]OTf, [Ir (cod)]BF 4, [Ir(cod)]ClO 4,[Ir(cod)]PF 6,[Ir(cod)]SbF 6, [Ir(cod)]BPh 4, [Ir (cyclooctadiene)]B{3,5-(CF 3) 2 C 6 H 3) 4, [Ir(nbd)]OTf, [Ir(nbd)]BF 4, [Ir (nbd)]ClO 4, [Ir(nbd)]PF 6, [Ir(nbd)]SbF 6, [Ir (nbd)]BPh 4, [Ir (nbd)]B{3,5-(CF 3) 2 C 6 H 3} 4, or [Ir(n-allyl) ((C,O)-substituted-benzoate)], wherein L is a ligand selected from: (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)dimethylamine (MonoPhos); (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)benzyl(methyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4-yl)-(1-phenylethyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)bis(1-phenylethyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4-yl)-2,5-diphenylpyrrolidine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)morpholine (Morfphos); and (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)piperidine (PipPhos);and (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)dimethylamine (MonoPhos); (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)benzyl(methyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4-yl)-(1-phenylethyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)bis(1-phenylethyl)amine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4-yl)-2,5-diphenylpyrrolidine; (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)morpholine (Morfphos); and (3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']dinaphthalen-4- yl)piperidine (PipPhos);and wherein PG is represented by the following formula: wherein Ar 1 is a C 6-14 aryl group optionally substituted by C 1-6 alkoxy; Ar 2 is a C 6-14 aryl group optionally substituted by C 1-6 alkoxy. Ar 1 is a C 6-14 aryl group optionally substituted by C 1-6 alkoxy; Ar 2 is a C 6-14 aryl group optionally substituted by C 1-6 alkoxy.