The Discovery Of Novel Ansamycins And Hybrid Terpenoids Drived By Biosynthetic Hypothesis

Secondary metabolites from the mutants of two actinomycetes LZ35 and SO 10 with the potential of producing ansamycins were chemically investigated.By a series of conventional purification techniques in laboratory,a total of 88 compounds including 54 new ones were obtained.The structures of the isolated compounds were determined on the basis of UV,MS,NMR and X-Ray single crystal diffraction.Some of these compounds were tested for their biological activities.28 compounds(1-28)were isolated from the 100 liter oatmeal medium of mutant SR201nam1OE,including seven new naphthalene neoansamycins D-I(10-15),four new macrolide compounds meridamyicns A-D(2-5)and two new diterpene cyclootatins L6-7(7-8).The isolation of compounds 10-15 further proved the gene nas is the biosynthesis gene cluster of novel octaketide naphthalenic ansamycins,and these compounds established foundation to study the specific biosynthesis pathway in the next step.To study the formation of the monoterpene cyclization in these quinolinecarboxamides,three mutants SP302,SP304 and SP305 were constructed respectively through knock out of OMT,CMT and P450 on the basis of the mutant LZ35A8.From the oatmeal medium of the three mutants on the above mentioned,23 compounds(29-33,36-45 and 49-51)were isolated including 15 new hybrid isoprenoids quinolinecarboxamides 29-33,36-42 and 49-51.After the optimization culture medium of S010,M5 solid medium was selected to cultivate the strain SO 10.10 compounds(52-61)were isolated from the M5 medium of the strain SO 10,including 5 new compounds,but without ansamycins.In our research group,the genetic characteristics of strain LZ35 is relatively thorough.Aim to obtain the pentaketide ansamycins from strain S010,the mutant SP301 was constructed by the heterologous expression of the pentaketide ansamycins gene cluster tpt in the mutant LZ35A8 with distinct genetic background.14 compounds(62-75)were isolated from the 30 liter oatmeal medium of mutant SP301,including ten new compounds,but without ansamycins.Then the mutant SP101 was constructed by promoter replacement of the PKS upstream on ansa gene cluster tpt.From the YMG medium of the mutant SP101,13 compounds(76-88)were isolated including 5 new pentaketide ansamycins tetrapetalones E-I(76-80).The isolation of compounds 76-80 further proved the gene tpt is the biosynthesis gene cluster of novel pentaketide ansamycins,and these compounds established foundation to study the specific biosynthesis pathway in the next step.