A highly stereospecific synthesis of (R)- and (S)-[2-2H1]glycine
Chirally pure [2-2H1]glycines were synthesised by the following sequence: O-benzylserine (4)→ 3-benzyloxy-2-bromopropionic acid (5)→ 3-benzyloxy[2-2H1]propionic acid (6)→ 3-benzyloxy[2-2H1]propionamide (7)→ 2-benzyloxy[1-2H1]ethylamine (8)→ 2-benzyloxy-N-phthaloyl[1-2H1]ethylamine (9)→ 2-hydroxy-N-phthaloyl[1-2H1]ethylamine (10)→[2-2H1]glycine (13). The isotopic, chemical, and optical purity of these compounds was determined by microanalyses and mass, n.m.r., and o.r.d. spectra. Complete retention of configuration in the first and second steps was established by correlation with (S)-(–)-2-bromopropionic acid and by conversion into (+)-(S)-[2-2H1]propionic acid, respectively. (S)-O-Benzyl[2-3H1]serine was made, and can be used to prepare (S)-[2-3H1]glycine.