Synthesis and physicochemical properties of [19, 20-13C]-17α-ethinylestradiol

13C2-17α-ethinylestradiol (13C2-EE2) was synthesized from estrone and 13C2-C2H2-gas to measure the metabolic clearance rate and the plasma concentration of 17α-ethinylestradiol (EE2) in tall girls, who are treated with high dosages of this estrogen. Interesting characteristics determined by (i) MS: the molecular ion m/z 298.183 is the only labelled ion in the spectrum, and by (ii)1H-NMR δ(ppm) 2.96 (dd, 1J(13C-H)=249 Hz, 2J(13C-H)=49.6 Hz; 1H; H20) and (iii) 13C-NMR δ 88.8(dd, 1J(13C-13C)=166 Hz, 2J(13C-H20)=49.8 Hz; C19); 80.2 (dd, 1J(13C17-13C19)= 73 Hz, 2J(13C17-13C20)=12.3 Hz; C17) and 74.6 (dd, 1J(13C-13C)=166 Hz, 1J(13C-H)= 249 Hz; C20) confirm the synthesis and structure of 13C2-EE2.