Method for preparing treprostinil and intermediate therefor

A method for preparing a compound of the following formula (9), which comprises a step of subjecting a compound of the following formula (8) to intramolecular Friedel-Crafts allylic alkylation:

• wherein,
• represents a single or double bond between carbon atoms,
• R1 represents hydrogen or a halogen,
• Y represents α-OR5:β-H or α-H:β-OR5,
• R5 represents hydrogen, and
• Z represents a C1-C6 alkyl group.

A method for preparing a compound of the following formula (10), which comprises a step of subjecting a compound of the following formula (9) to hydrogenation:

• wherein,
• represents a single or double bond between carbon atoms,
• R1 represents hydrogen or a halogen,
• Y represents α-OR5:β-H or α-H:β-OR5,
• R5 represents hydrogen, and
• Z represents a C1-C6 alkyl group.

A method for preparing a compound of the following formula (1), which comprises the steps of:

• (vii) subjecting a compound of the following formula (9) to hydrogenation to obtain a compound of the following formula (10);
• (viii) subjecting the compound of the following formula (10) to alkylation with a compound of the following formula (11) to obtain a compound of the following formula (12);
• and
• (ix) hydrolyzing an ester group of the compound of the following formula (12) to give the compound of formula (1):
• wherein,
• represents a single or double bond between carbon atoms,
• R1 represents hydrogen or a halogen,
• R3 represents a C1-C6 alkyl group,
• Y represents α-OR5:β-H or α-H:β-OR5,
• R5 represents hydrogen,
• Z represents a C1-C6 alkyl group, and
• X′ represents a halogen.