Patent ID: 8198484

Claim:
A labeled compound of the formula where C* are each 13 C, X is selected from the group consisting of —NR 6 R 7 and —OR 8 wherein R 6 and R 7 are each independently selected from the group consisting of C 1 -C 4 lower alkyl, alkoxy and aryl and R 8 is selected from the group consisting of C 1 -C 4 lower alkyl, alkoxy and aryl, and T is selected from the group consisting of —CH 3 , —CD 3 , —CH 2 —S—R 9 , —CH 2 —S(O)—R 9 , and —CH 2 —(O)S(O)—R 9 wherein R 9 is an aryl group selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure wherein R 1 , R 2 , R 3 , R 4 and R 5 are each independently selected from the group consisting of hydrogen, a C 1 -C 4 lower alkyl, a halogen, and an amino group from the group consisting of NH 2 , NHR and NRR′ where R and R′ are each independently selected from the group consisting of a C 1 -C 4 lower alkyl, a phenyl and an alkoxy group.