In 1928, F. Went discovered the first plant hormone) and shortly after in 1933 F. Kogl and his co-workers isolated the compounds in crystalline forms and named them "auxins". In 1934, they reported the constitutions of auxins a (I) and b (II) .?),3) However, thereafter none has succeeded to re-isolate them by the same procedures from the same kinds of materials as were used by F. Kogl and his co-workers. The authors considered, if the proposed structures of auxins a and b are correct, the synthetic compounds having their structures must have biological activity as declared by F. Kogl et al. They took up auxin b as the synthetic target, because it has two less asymetric carbon atoms than auxin a. In 1966 the authors synthesized the stereoisomeric mixture of the o-lactone (III) of compound (II) proposed for auxin b by F. Kogl4> >~> and tested its activity on the premise that in extremely dilute aqueous solution, the lactone will afford auxin b itself by ring opening. However it did not show any biological activities as Kogl et al. declared.6) Shortly after, J. A. Vliegenthart and J. F. G. Vliegenthart reported7) that they re-investigated the samples of auxins a and b and relating compounds in the sample tubes left by Kogl in his laboratory and they found that the contents were totally different from the compounds reported by him and his co-workers. For example, the substance in the sample tube labeled "auxin a" was cholic acid, that labeled "auxin a lactone" was p-hydroquinone, that labeled "auxin b" was thiosemicarbazide etc. However, curiously the melting points of them are almost identical with those of the compounds in the reports of Kogl et al. Recently K. Buffel reexamined the reports relating to auxins by F. Kogl and his co-workers and other researchers. He newly proposed a structure (IV) as the most probable one for auxin b.8) The authors synthesized the compound (IV) and the isomeric compound (V) without any stereo-control. The first product theoretically contains the "natural auxin b" to the amount of one thirtysecond of it. However, to the authors' great regret, the both synthesized materials (IV) and (V) did not show any biological activities as F. Kogl stated. The biological tests were done by T. Nakamura and her co-workers and their details will be reported in separate papers.
One of us and a co-worker discovered that a simple compound, the allethronyl ester of 2,2,3,3-tetramethylcyclopropanecarboxylic acid (I)1*, had the equal or higher insecticidal activity to those of chrysanthemic esters, and also that 2,2-dichloro-3,3-dimethylcyclopropanecarboxylic acid ( 2) esters2) had a half or less order of activity. On the other hand, Elliott et al.3) found that the acyano-3-phenoxybenzyl ester of 2,2-dimethyl-3(2,2dibromovinyl)cyclopropanecarboxylic acid (3, decamethrin), was the most active pyrethroid insecticide. So it is interesting to investigate the synthesis and insecticidal activity of 2,2-dibromo-3,3-dimethylcyclopropanecarboxylic acid (4) ester, acid 3 corresponding to a vinylogue of acid 4. Meanwhile, Miyakado et al.A) reported that aisopropyl(4-chlorophenyl)acetic acid, the acid moiety of a pyrethroid (fenvalerate),resembled in steric structure that of chrysanthemic acid. Therefore, it is also interesing to examine the activities of esters of bicyclo [2,2,l]heptenecarboxylic acids (5 and 6), these acids seeming to be similar to the acid 1 in steric structure.
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