Deuterium labeling of diethylstilbestrol and analogues

E-2,2,3',3″,5,5,5',5″-octadeuteriodiethylstilbestrol (DES-d8) and Z-2,3',3″,4,5,5,5',5″-octadeuterio-3,4-bis(p-hydroxyphenyl)-2-hexene (ψ-DES-d8) were synthesized from E-diethylstilbestrol (DES) by hydrogen/ deuterium exchange in a mixture of methanol-d and deuterium chloride in deuterium oxide. The structures, isotopic purity, and positions of up-take of deuterium were determined by nuclear magnetic resonance (NMR) and mass spectrometry (MS). Additional confirmation of the positions of deuterium exchange in stilbestrols was obtained from an analysis of the oxidation of DES-d8 to Z,Z-2,3',3″,5,5',5″-hexadeuteriodienestrol (β-DIES-d6) and of the hydrogen/deuterium exchange reaction of hexestrol (HEX) to 3',3″,5',5″-hexestrol (HEX-d4). Structural analysis and the determination of isotopic purity of the latter two compounds were also carried out by NMR and MS. The uptake of eight deuterium atoms by DES is postulated to proceed via two different reactions occurring simultaneously: 1. acid catalyzed deuteration of all four phenolic ortho-positions (3',3″,5',5″); 2. acid catalyzed deuteration of the olefin bridge with subsequent formation of deuterated ψ-DES (3 or 4). Due to the equilibration between DES, ψ-DES, and Z-diethylstilbestrol (cis-DES) in the acidic reaction mixture at 85°C, the deuterated ψ-DES is thought to rapidly rearrange to deuterated DES. Repeated deuteration will eventually form DES-d8 fully labeled in the 2,2,5,5 methylene positions.