Acid 3S, 4aR, 6S, 8aR 6 - (((2S) -2- (carboxyl) -4,4-difluoropyrrolidinyl) methyl-1,2,3,4,4a, 5,6,7,8,8a- Decahydroisoquinoline-3-carboxylic acid and its esters for the treatment of migraine, its use and pharmaceutical compositions
1. A compound of formula wherein R 1 and R 2 are independently a hydrogen or C 1 -C 20 alkyl, or a pharmaceutically acceptable salt thereof. 5. Use of a compound as defined in claim 1 in the manufacture of a medicament for the treatment of migraine. 7. A pharmaceutical composition for the treatment of migraine, characterized in that it comprises a compound as defined in claim 1 in combination with a pharmaceutically acceptable carrier, diluent or excipient.