(2S, 3R) -2-Amino-3- (3, 4-dihydroxyphenyl) -3-hydroxypropionic acid (L-DOPS) (1) was efficiently labeled with carbon-14 at the 3-position of the propionic acid moiety for use in mammalian metabolic studies. The synthesis was achieved according to the scheme illustrated in Fig. 2. Condensation of 3, 4-bis (benzyloxy) [carbonyl-14C] -benzaldehyde (7) with the optically active 5-oxazolidinone (8) gave the optically active alcohol (9) . Catalytic hydrogenation of 9 under acidic condition afforded 1. The overall yield of 1 was 74% from 7.
We examined the safety and the clinical usefulness of oxygen-15 water produced by the automated synthesis system (Sumitomo Heavy Industries, type 01) by means of positron emission tomography (PET) . This clinical trial involved 60 patients with various diseases. No side effects were observed by subjective and objective symptoms, physical findings, and laboratory tests. In all 60 cases, the PET images of good quality were obtained. In 95% of the cases, PET provided equivalent or better clinical information compared with other clinical examinations. The overall assessment of the clinical usefulness demonstrated that the method was useful or extremely useful in 59 cases (98%) .