C-14 labelling of NVPVID400 - a specific vitamin D-3-hydroxylase inhibitor

The synthesis and analysis of [C-14]NVP VID400 (1) under bar, a specific vi tamin D-3-hydroxylase inhibitor is reported. The key intermediate is (R)-2- amino-1-phenyl-[1-C-14]ethanol 9 synthesized in an effective, enantioselect ive approach using a borane reduction of phenacyl chloride (6) under bar in the presence of (R)-oxazaborolidine-catalyst (2) under bar. After N-acylat ion of (9) under bar the resulting amide <(10)under bar> was converted to t he oxazoline <(12)under bar>, which when treated with imidazole ring-opened to the title compound (1) under bar. Both reactions - ring-closure and rin g-opening - went with complete configurational inversion. The secondary iso tope effect induced splitting of C-13-NMR signals enabling the quantificati on of the isotopic purity and thereby the specific activity of (1) under ba r.