Synthesis And Larvicidal Activity Against Mosquito Species Of Phrymarolins Derivatives

The herbaceous perennial plant, Phryma leptostachya L., is the sole species of the familyPhrymaceae. P. leptostachya has been shown to be rich of lignans and has significantinsecticidal activity against various insect species. Phrymarolins I is the representativemember of the lignans isolated from this plant and showed high larvicidal activity against theearly fourth instar larvae of Culex pipiens pallens. In an attempt to clarify corelationshipbetween chemical construction and insecticidal activities of Phrymarolins I and its derivatives,series of Phrymarolins derivatives were synthesized via structure modification. And theinsecticidal activity against the early fourth instar larvae of Culex pipiens pallens was studiedusing these compounds. The contents and results were summarized as follows:1. By ester hydrolysis reaction, the experiment take the Phrymarolins I as lead compoundto get the key intermediate compound A. All four series of42unreported Phrymarolinsderivatives shown in the formula （Ⅰ）,（Ⅱ）,（Ⅲ） and（Ⅳ） were synthesized via a simplemodification with etherification, esterification, click chemisty （copper-catalyzed azide-alkynecycloaddition）and barton-mccombie deoxygenation, and their structures were identified by¹H-NMR,¹³C-NMR, DEPT, MS and IR.2. Taking Phrymarolins I as positive control, the insecticidal activities of Phrymarolinsderivatives against the4rdinstar larvae of Culex pipiens pallens were tested. The resultsshowed that the insecticidal activity of tested compounds varied with their substituted groupsevidently. Ester and triazole derivatives showed lower insecticidal activity than PhrymarolinsI. While, the insecticidal activity of GP-â…£, GP-12, GP-14, GP-15, GP-19, and GP-21wereshowed obviously higher than Phrymarolins I.3. Based on the results of the preliminary insecticidal activity tests, further tests onGP-12, GP-14, GP-15, GP-19, GP-21and GP-IV were taken. The results showed thatGP-21, GP-14, and GP-12showed high larvicidal activity, for which the LC₅₀values wereestimated at1.37,1.61mg/L, and1.75mg/L against the early fourth instar larvae of Culexpipiens pallens, respectively.4. Preliminary structure-activity relationship analysis indicated that the insecticidalactivity of tested compounds varied with their substituted groups evidently. The insecticidal activity of the derivatives with bigger substituent at11-C are obviously lower than that withsmaller substituent. In addition，derivatives containing ether substituted are much better thanthat containing carboxylate ester.