Norethindrone acetate (NA) and ethinyl estradiol (EE) related oxidative transformation products in stability samples of formulated drug product: synthesis of authentic references

Abstract Preparative chemical methods for the synthesis of eight oxidative transformation products of ethinyl estradiol (EE) and norethindrone acetate (NA) are described. The prepared materials are useful as reference materials and standards for pharmaceutical analysis of EE and NA as bulk chemical or in formulated product. All eight products result from oxidation of the A and/or B rings of the parent compounds. Oxidation of the heteroannular 3,5 dienyl acetate derivative of NA resulted in the 6α-hydroxy, 6β-hydroxy and 6-keto NA. Oxidation of 6-keto NA led to the preparation of 6α-hydroxy, 6β-hydroxy, 6-keto- and Δ 6 EE. Δ 11 EE was prepared from estrone.