Studies Of The Sapogenin Utilization In Synthesis Of Natural Products

Steriods is unique and considered as the" key of life". The dissertation focuses on the sustainable utilization of the abundant steroids resources in synthesis of natural products. There are three main parts:First, the study of synthesis of dihydropennogenin. Comparing the dihydropennogenin with tigogenin, dihydropennogenin has 17-hydroxy, while tigogenin doesn't. For utilization the untouchable skeleton of sapogenin, we started from tigogenin , through oxidation , opening of E, F ring, turning 16-carbonyl into sulfide ketal , then sulfide enol emer,reduction of sulfide enol ether by Raney-Ni, 3,26-diacetoxylcholestan-16-ene-22-one was obtained in overall yield of 35.9%; and then 3,26-dihydroxycholestan-16-ene-22-one under the condition of K2CO3/CH3OH, the crude product obtained from epoxidation of the compound by mCPBA, was catalysed by pTSA.H2O in order to close the E, F ring by intramolecular opening of 16,17 epoxy. Unfortunately we couldn't obtained the target molecular, since the 1HNMR-spectra was hard to be elucidated due to the existence of epimer. We chose dihydroxylation of 16, then hydrolysised the 3,26 acetic ester, but a compound which 16-hydroxy turned into 16-ketone was obtain instead of the target molecular, through intramolecular reaction catalysed by pTSA.H2O. Deoxidization of the 22-ketone of 3,26-diacetoxylcholestan-16-ene-22-one, epoxidation by mCPBA 3,26-di hydroxylcholestan-16, 17-epoxide-22-alcohol was obtained. Further research will be continuated.Second, synthesis of 12(13)-seco-steroid sapogenin. hecololactone 3-acetate was obtanined by Baeyer-Villager oxidation of hecogenin 3-acetate under thecondition of cat. H2SO4(con), CH3CO2H and CH3CO3H which was prepared by Ac2O and 30% H2O2 at 30~40C for six hours. Hecoloactone 3-acetate was reduced by Lithium aluminum hydride to hecolyl alcohol, then dehydrated by HC1 (38%) tol2-hydroxy-13(14)-ene-12(13)-seco-hecogenin.Third, preparation the key intermediate for the study of total synthesis of North Hemisphere of Cephalostatin 1. 14,16-diene-bisnorcholane- 22-alcohol was obtained starting from hecogenin in overall yield of 30.5% after eleven steps.