Facile green synthesis of 16-dehydropregnenolone acetate (16-DPA) from diosgenin

ABSTRACT

Chromium- and MnO₂-free green synthesis of industrially important steroidal drug intermediate 16-dehydropregnenolone acetate (16-DPA) starting from diosgenin is reported. The reaction sequence involves three steps: acetolysis followed by acetylation, oxidation, and hydrolysis. In the first step, Ac₂O was used both as reagent and solvent in combination with a Lewis acid (AlCl₃), which led to considerable reduction of high temperature and pressure requirements of earlier processes. The oxidation step was made catalytic with the use of KMnO₄(5 mol%) in the presence of co-oxidant NaIO₄, leading to less waste generation (of chromium, MnO₂, etc.). Minimization of the temperature, pressure, time consumption, and use of nontoxic solvents makes the process very handy and simple.

GRAPHICAL ABSTRACT

KEYWORDS:

• 16-DPA
• diosgenin
• green synthesis

Acknowledgments

The authors acknowledge the director, CSIR–NEIST, Jorhat, Assam, and Pallab Pahari for their kind help.