Synthesis of

1234 5 14 214 14 14 The present invention is directed to labeled compounds of the formulae wherein R, R, R, Rand Rare each independently selected from the group consisting of hydrogen, a C-Clower alkyl, a halogen, and an amino group selected from the group consisting of NH, NHR and NRR′ where R and R′ are each independently selected from the group consisting of a C-Clower alkyl, an aryl, and an alkoxy group, and X is selected from the group consisting of hydrogen, a C-Clower alkyl group, and a fully-deuterated C-Clower alkyl group.