The Synthesis of the Steroidal Sapogenins^1,2

An alternative total synthesis of solamargine

“…After coupling of glycosyl donor 5 and aglycone precursor 7 in anhydrous methylene chloride with mild catalyst AgOTf [9], key intermediate 8 was obtained in 94% isolated yield. Selective reduction of 16-ketone 8 with NaBH 4 /i-PrOH [10] (9), followed by reductive cyclization with Ph 3 P/THF/H 2 O under refluxing (10) and removal of the acetyl group with NaOMe in MeOH, afforded acceptor 11 in 53% overall yield for three steps [8]. Condensation of 11 and rhamnopyranosyl bromide 12 using AgOTf and 2,6-lutidine as catalysts [11] afforded trisaccharide alkaloid 13 in excellent yield (90%).…”

ß-Alkoxy-α,ß-unsaturated ketone systems in steroidal frameworks, and their conversion to 23,24- bisnorcholane lactones

“…Bisnorcholanic lactones 10, and 11, are important synthetic intermediates that have been used in the synthesis of sapogenins, 11 and brassinosteroid analogues. 12 Despite their usefulness no practical method has been developed to produce them in high quantities; only small quantities have been obtained by different reactions 13 or by plant extraction.…”

Bc → Abc → Abcd

“…Furthermore, epiandrosterone was the starting material for the synthesis of tigogenin (23, R = H, R' = Me) and neotigogenin (23, R = Me, R' = H), typical members of the large and important family of steroidal sapogenins [18]. The synthesis of these two compounds, in turn, constituted the total synthesis of a number of sapogenins including diosgenin, gitogenin, smilagenin, and hecogenin, because of their known interconversions.…”