Increased interest in nonradioactive labels for use as general biological probes had led us to develop efficient methods for labeling the nicotinamide (1) portion of NAD+ We have described facile pyridine syntheses in which nicotinamide can be labeled (13C, 2H, 15N) at the 1, 2, 3, 6, and carbonyl positions and then be biosynthetically incorporated into the coenzyme NAD+.* However, these methods were not useful for labeling the 4 position of ...
