acetoxy-17,17-ethylendioxy-15β,16β-methylene-5-androsten-7β-ol（Ⅰ） was prepared by 3 steps from 3β-acetoxy-15β,16β-methylene-5-androsten-17-one （Ⅱ） with overall yield of 52.7%. Thus, interaction of ethylene...acetoxy-17,17-ethylendioxy-15β,16β-methylene-5-androsten-7β-ol（Ⅰ） was prepared by 3 steps from 3β-acetoxy-15β,16β-methylene-5-androsten-17-one （Ⅱ） with overall yield of 52.7%. Thus, interaction of ethylene glycol and material （Ⅱ） gave 3β-acetoxy- 17,17-ethylendioxy-15β,16β-methylene-5-androsten （Ⅲ） which was subsequently oxidated and stereoselectively reduced to produce compound（Ⅰ）. The normal influencing factors, such as the types of oxidants and reductives, the mole ratio of reactants, the reaction temperature, and the addition ways of reactants, in oxidation and reduction were discussed. The results show that the oxidation rate order is CrO3-C5H5N （1∶1, mole fraction）>CrO3-C5H5N（1∶2）>（C5H5NH）2Cr2O7 in terms of the oxidant, the yield of the oxidation becomes higher with increasing the oxidant stoichiometry and raising the reaction temperature. And the optimum condition is that the reaction temperature is at 30 ℃, and n （Ⅲ）/ n （CrO3-C5H5N（1∶2））=1∶20. The yield of the -7β alcohol order with Li[Al（OC（CH3）3）3H] （e.g.78.6%） is more than that with NaBH4 （e.g.14.5%） in terms of the reductive （agent） and the reduction rate decreases in the course of reaction. The compound （Ⅰ） is characterized by IR and MS.展开更多
Zea mays(maize)is an important agricultural crop that produces a variety of valuable terpenoids,including several triterpenoids.However,no oxidosqualene cyclase(OSC)enzymes,which catalyze the first step in triterpenoi...Zea mays(maize)is an important agricultural crop that produces a variety of valuable terpenoids,including several triterpenoids.However,no oxidosqualene cyclase(OSC)enzymes,which catalyze the first step in triterpenoid biosynthesis,have been identified in maize.Here,we identified a novel OSC(ZmOSC1)in maize using a combination of genomic mining and phylogenetic analyses.To functionally characterize the candidate OSC,we constructed a yeast strain that produced high levels of 2,3-oxidosqualene.When ZmOSC1 was expressed in this strain,three compounds were detected and identified as hop-17(21)-en-3-ol,hopenol B and simiarenol,respectively.For their biosynthesis,we proposed a potential cyclization mechanism catalyzed by ZmOSC1 via the generation of a dammarenyl cation,followed by sequential cationic ring expansion,cyclization,cationic migration and further proton elimination.This study discovered and characterized an OSC from maize for the first time,and laid a foundation to produce three bioactive pentacyclic triterpenes,hop-17(21)-en-3-ol,hopenol B and simiarenol,using synthetic biology approaches.展开更多
文摘acetoxy-17,17-ethylendioxy-15β,16β-methylene-5-androsten-7β-ol（Ⅰ） was prepared by 3 steps from 3β-acetoxy-15β,16β-methylene-5-androsten-17-one （Ⅱ） with overall yield of 52.7%. Thus, interaction of ethylene glycol and material （Ⅱ） gave 3β-acetoxy- 17,17-ethylendioxy-15β,16β-methylene-5-androsten （Ⅲ） which was subsequently oxidated and stereoselectively reduced to produce compound（Ⅰ）. The normal influencing factors, such as the types of oxidants and reductives, the mole ratio of reactants, the reaction temperature, and the addition ways of reactants, in oxidation and reduction were discussed. The results show that the oxidation rate order is CrO3-C5H5N （1∶1, mole fraction）>CrO3-C5H5N（1∶2）>（C5H5NH）2Cr2O7 in terms of the oxidant, the yield of the oxidation becomes higher with increasing the oxidant stoichiometry and raising the reaction temperature. And the optimum condition is that the reaction temperature is at 30 ℃, and n （Ⅲ）/ n （CrO3-C5H5N（1∶2））=1∶20. The yield of the -7β alcohol order with Li[Al（OC（CH3）3）3H] （e.g.78.6%） is more than that with NaBH4 （e.g.14.5%） in terms of the reductive （agent） and the reduction rate decreases in the course of reaction. The compound （Ⅰ） is characterized by IR and MS.
基金This work was financially supported by the National Key Research and Development Program of China(Grant Nos.2020YFA0907900&2019YFA0905700)the National Science Resource Investigation Program of China(2019FY100100)+2 种基金the international Partnership Program of Chinese Academy of Sciences(153D31KYSB20170121)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB27020206)the Strategic Biological Resources Service Network Plan of the Chinese Academy of Sciences(Grant No.KFJ-BRP-009&KFJ-BRP-017-60).
文摘Zea mays(maize)is an important agricultural crop that produces a variety of valuable terpenoids,including several triterpenoids.However,no oxidosqualene cyclase(OSC)enzymes,which catalyze the first step in triterpenoid biosynthesis,have been identified in maize.Here,we identified a novel OSC(ZmOSC1)in maize using a combination of genomic mining and phylogenetic analyses.To functionally characterize the candidate OSC,we constructed a yeast strain that produced high levels of 2,3-oxidosqualene.When ZmOSC1 was expressed in this strain,three compounds were detected and identified as hop-17(21)-en-3-ol,hopenol B and simiarenol,respectively.For their biosynthesis,we proposed a potential cyclization mechanism catalyzed by ZmOSC1 via the generation of a dammarenyl cation,followed by sequential cationic ring expansion,cyclization,cationic migration and further proton elimination.This study discovered and characterized an OSC from maize for the first time,and laid a foundation to produce three bioactive pentacyclic triterpenes,hop-17(21)-en-3-ol,hopenol B and simiarenol,using synthetic biology approaches.
