STEROLS. LXXXI. CONVERSION OF SARSASA-POGENIN TO PREGNANEDIOL-3(α),20(α)

A Simple Efficient Process for the Synthesis of 16-Dehydropregnenolone Acetate(16-Dpa)–A Key Steroid Drug Intermediate from Diosgenin

“…are synthesized from 16-dehydropregnenolone acetate (16-DPA) 1, barring a few which are obtained by total synthesis. The plant origin compounds solasodine 2 and its oxygen analogue diosgenin 3 ( Figure 1) are the two main ingredients from which 16-DPA is generally synthesized [4][5][6][7][8][9][10][11][12][13][14][15]. Due to the favorable climatic condition of North East region of India, diosgenin yielding dioscorea species of plants, viz., D. compositae and D. floribunda grow abundantly in the region which led us to investigate commercial exploitation of these plants through large scale production of 16-DPA starting from diosgenin.…”

“…Synthesis of 16-dehydropregnenolone acetate (16-DPA) 1 from solasodine 2 and diosgenin 3 has been reported by several workers in various literatures [4][5][6][7][8][9][10][11][12][13][14][15]. For the conversion of this spirostanic compound, diosgenin (22-iso-5-spirostane-3β-ol) into 16-DPA (3β-acetoxy-pregn-5,16-diene-20-one) 1, it must be isomerized first to furostenol derivative pseudodiosgenin diacetate (3β,26-diacetoxyfurosta-5,20(22)-diene) 4, through acetolysis (Figure 2), which on subsequent oxidation of the 20(22) enolic double bond followed by hydrolytic degradation furnishes 16-DPA [4][5][6][7][8][9][10][11][12][13][14][15].…”

“…For the conversion of this spirostanic compound, diosgenin (22-iso-5-spirostane-3β-ol) into 16-DPA (3β-acetoxy-pregn-5,16-diene-20-one) 1, it must be isomerized first to furostenol derivative pseudodiosgenin diacetate (3β,26-diacetoxyfurosta-5,20(22)-diene) 4, through acetolysis (Figure 2), which on subsequent oxidation of the 20(22) enolic double bond followed by hydrolytic degradation furnishes 16-DPA [4][5][6][7][8][9][10][11][12][13][14][15]. Chemical transformations of spirostanic compounds also find importance towards the synthesis of plant growth promoting substances including ecdysteroids and some furostenols having significant phytotoxicity [18].…”

“…Chemical transformations of spirostanic compounds also find importance towards the synthesis of plant growth promoting substances including ecdysteroids and some furostenols having significant phytotoxicity [18]. Marker's degradation is the earliest known process for converting diosgenin into 16-DPA [5][6][7].…”

“…The condition of the isomerization reaction of diosgenin 3 as reported by Marker et al involved the direct use of acetic anhydride at an elevated temperature and pressure in a sealed tube, while the use of high boiling anhydrides as solvent led to lower yield of the isomerized product pseudodiosgenin diacetate 4 [5][6][7].…”