An Investigation Into The Synthesis Of Important Steroidal Intermediates From DHEA

Brassinosteroids(BRs) is a new kind of plant growth regulators, and it hasremarkable biological activities. Nowadays they are widely used in the agriculture indeveloped countries. The content of brassinosteroids in natural plants is very low andchemical synthesis of BRs is the indispensable foundation to promote their wideapplication. Then the synthesis of brassinosteroids and their intermediates becomeshotspot now. In recent years, the price of dehydroandrosterone fell obviously and theresearch of the synthesis of brassinosteroids and their important intermediates fromDHEA is nearly in blank state. For this reason, two new routes for synthesis ofbrassinosteroids from DHEA were designed and steroidal ester-one of theintermediates was successfully synthesized. At the same time, the side chainingraftation of DHEA was achieved at the position of C-17 and methylene, ethylene,methoxy-methylene and ester group were successfully introduced into DHEA.3-p-Toluenesulfonyldehydroandrosterone(A) was prepared by esterification fromDHEA first of all and this ester was turned to steroid B by alkaline hydrolysis. Thewhole yield of the above two steps was 60.8%. Steroid B reacted with O,O-diethyl-ethoxy-carbonyl-α-methyl-methylene phosphonate ester by improvedWittig reaction to get steroid C with a yield of 5.0%.Ethidene was introduced at the position of C17 of DHEA by Wittig reaction to getsteroid D. When potassium tert-butoxide was used as alkali, the reaction reached theyield of 95.0%;sodium hydride being as alkali and the yield 66.0%. Steroid D wasesterified by toluene-p-sulfonic acid to get steroid E with a yield of 90.0%. DHEA reacted with triphenylmethyl phosphonium iodide, (methoxymet-hyl)triphenylphosphorus chloride and triphenyl-ethoxy-carbonyl-methylene phos-phonate ester by Wittig reaction respectively to introduce methylene (steroid G),methoxymethylene (steroid H) and ethoxycarbonyl methylene (steroid I) into DHEAsuccessfully . Their corresponding yields were 95.0%,10.0% and 53.0%. The structures of the key intermediates and the novel target compounds wereconfirmed by the analysis of IR ,NMR and MS datum.