Method for preparing 15-keto-prostaglandin E derivative

1. A method for preparing a 15-keto-prostaglandin E derivative represented by formula (I):

wherein,

R 1 is a saturated or unsaturated bivalent lower or medium aliphatic hydrocarbon residue, which unsubstituted or substituted with halogen, lower alkyl, hydroxy, oxo, aryl or heterocyclic, and at least one of carbon atom in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur;

R 2 is a saturated or unsaturated lower or medium aliphatic hydrocarbon, which is unsubstituted or substituted with lower alkyl, lower alkoxy, lower alkanoyloxy, cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclic or heterocyclicoxy group; cyclo(lower)alkyl; cyclo(lower)alkyloxy; aryl; aryloxy; heterocyclic; or heterocyclicoxy group;

B is —CH 2 —CH 2 —, —CH=CH— or —C═C—;

Q is —CH 3 , —COCH 3 , —OH, —COOH or a salt, ether, ester or amide thereof;

X 1 and X 2 are hydrogen, lower alkyl, or halogen;

which comprises the step of hydrolyzing the compound represented by formula (II):

wherein,

A 1 is a protecting group for hydroxy group, R 1 , R 2 , B, Q, X 1 and X 2 are the same as above in the presence of phosphoric acid compound.

2. The method of claim 1 , wherein at least one of X 1 and X 2 is halogen.

3. The method of claim 1 , wherein both of X 1 and X 2 are halogen.

4. The method of claim 1 , wherein X 1 and X 2 are fluorine.

5. The method of claim 1 , wherein the phosphoric acid compound is phosphoric acid.

6. The method of claim 1 , wherein said step is conducted at a temperature from about 0° C. to 35° C.

7. The method of claim 1 , wherein the reaction time of said step is about 1 to 6 hours.