Patent ID: 6932961

Claim:
An isotopically labeled compound of formula I or a pharmaceutically acceptable salt or enantiomer thereof wherein R 1 is (a) H, or (b halo; R 2 is (a) H, or (b) C 1-6 alkyl; R 3 is (a) —(CH 2 ) m —NR 8 R 9 ; R 4 is (a) aryl; aryl is phenyl or naphthyl, optionally substituted with one or more R 10 ; Each R 8 and R 9 is independently (a) H, (b) C 1-6 alkyl optionally substituted with —OH, (c) CHO, provided that only one of R 8 and R 9 is CHO and the other is H, and (d) R 8 and R 9 taken together with the nitrogen to which they are attached form a five-, six-, or seven-membered heterocyclic ring wherein the heterocyclic ring contains an additional heteroatom N(Y); Y is H or C 1-6 alkyl; R 10 is (a) halo, (b) —OH, (c) —CN, (d) —CF 3 , (e) C 1-6 alkyl, or (f) —NH 2 ; and m is 2, 3 or 4; and wherein the compound of formula I contains an isotopic label, wherein one or more atoms have an atomic mass or mass number different from the atomic mass or mass number usually found in nature, and wherein the atoms are hydrogen, carbon, nitrogen, oxygen, fluorine, iodine, and chlorine.