Complete ¹H NMR Assignment of Diosgenin Benzoate

Diosgenin (1a) is used as a raw starting material for the synthesis of steroid hormones and contraceptives and is probably one of the most commercially important steroidal sapogenins. The literature on 1a is extensive, and topics range from its isolation from a variety of natural sources to its chemical modifications and therapeutic properties as an anti-cancer, anti-diabetic, anti-thrombosis, anti-inflammatory, and anti-viral agent, among others.( 1) The spectroscopic characteristics of 1a have been analyzed for a long time, but the assignment of the complete H-1 NMR profile remains incomplete due to the overlapping signals obtained with the most common spectrometers. In the current study, the 750-MHz H-1 NMR spectrum of diosgenin benzoate (1b) has been completely assigned by means of QM-based H-1 iterative full spin analysis (HiFSA), which is used for the complete H-1 NMR description of intricate natural products and the quality control of pharmaceuticals.( 2) The complete assignment was facilitated by taking advantage of some chemical shifts described for 1a and the coupling constants of the cholestane skeleton of cholesteryl benzoate, which were also recently calculated by HiFSA.( 3)