Patent ID: 7612103

Claim:
A compound of formula wherein R 1 and R 1 ′ are hydrogen or deuterium, R 2 , R 3 and R 4 are hydrogen or deuterium, R 5 is the residue of an alpha amino acid, wherein the N which is part of the ring in formula I is acylated by the carboxylic group of said amino acid and wherein the carbonyl group of said amino acid is bound to the nitrogen of the group of formula and the —OH group of said amino acid function is missing, X is S or N-ALK, the group of formula is piperidinyl or tetrahydropyridinyl, ALK is (C 1-4 )alkyl, and R 6 is hydrogen, hydroxy or (C 2-12 )acyloxy, with the proviso that if the group is piperidinyl and X is S, then R 6 is other than hydrogen.