Method for preparing prostaglandin derivative

A method for preparing a prostaglandin derivative of formula (A):

• wherein A1 is a hydrogen or a protecting group for a hydroxy group;
• Y is —OA2, wherein A2 is a hydrogen or a protecting group of a hydroxy group;
• W is —R1-Q, wherein R1 is a saturated or unsaturated bivalent lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, lower alkyl, hydroxy, oxo, aryl or heterocyclic, and at least one of carbon atoms in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur, Q is —CH3, —COCH3, —OH, —COOH or a functional derivative thereof;
• or
• Y and W may both together form a group represented by the formula:
• wherein R1′ is a bivalent saturated or unsaturated lower to medium aliphatic hydrocarbon residue;
• R3 is a saturated or unsaturated lower to medium aliphatic hydrocarbon residue that is unsubstituted or substituted with a lower alkoxy, a lower alkanoyloxy, a cyclo(lower)alkyl, a cyclo(lower)alkyloxy, an aryl, an aryloxy, a heterocyclic or a heterocyclicoxy;
• a cyclo(lower)alkyl group;
• a cyclo(lower)alkyloxy group;
• an aryl group;
• an aryloxy group;
• a heterocyclic group;
• a heterocyclicoxy group;
• X1 and X2 are a hydrogen, a lower alkyl group or a halogen;
• and
• Z is ═CH— or —CH═CH—,
• provided that —OA1 and Q may together form
• which comprises reacting an aldehyde represented by formula (1):
• wherein Y, W and A1 have the same meanings as above;
• B is a single bond or —CH2—, with a 2-oxoalkyl phosphonate represented by formula (2):
• wherein X1, X2 and R3 have the same meanings as above;
• and
• R2 is a lower alkyl group;
• in a reaction solvent under the presence of a hydroxide selected from the group consisting of alkali metal hydroxide and alkaline earth metal hydroxide as sole base,
• wherein at least one of X1 and X2 is a halogen.