Synthesis of Some Novel 4-Acyl-3-Oxo-4-Aza-5-Pregnene-20 E -Oxime Ester Derivatives as Potent 5α-Reductase Inhibitors

3-Oxo-4-aza-5-pregnene-20E-oxime was synthesised from the starting material progesterone through oxidative ring cleavage, amination ring closure and oximation. The configuration of the oxime was determined from the 2D-NOESY spectrum. A series of oxime ester derivatives were obtained through the acylation of the oxime, their structures were confirmed by ESI-MS, ¹H NMR, ¹³C NMR and HRMS.