US Patent 7816546 Process for the synthesis of high purity

The invention relates to a process for the synthesis of d-(17α)-13-ethyl-17-hydroxy-18,19-dinorpregn-4-ene-20-yn-3-one-oxime (also known as norelgestromin) via acetylation of d-norgestrel at position 17; oximation of the oxo group at position 3 of the obtained d-(17α)-13-ethyl-17-(acetyloxy)-18,19-dinorpregn-4-ene-20-yn-3-one; and then hydrolyzing the acetyloxy group at position 17 of the obtained d-(17α)-13-ethyl-17-(acetyloxy)-18,19-dinorpregn-4-ene-20-yn-3-oxime derivative, thereby obtaining norelgestromin.