Kogls auxin-a and -b. the plant-growth promoters

Auxin-a and b share the same trisubstituted cyclopentene ring in their structures. The presence of that ring system was deduced by permanganate oxidation of auxin-a and b, which gave auxin-glutaric acid (D) as crystals. Starting from (.S )-3-methylpcntanoic acid, Kogl and Erxleben synthesized three possible stereoisomers of D, and proposed one of them to be identical with the acid derived from the natural products. 

The synthesis of these plant-growth promoters auxin-a and b was attempted by several groups. In 1966, Matsui (my former teacher) and Hwang synthesized a mixture of all of the possible stereoisomers of the 5-lactone E derived from auxin-b (C). The synthetic product, however, was biologically inactive. 

These analytical results by Vliegenthart together with the fact that no one could reisolate auxin-a and b, in addition to the fact that the synthetic E was biologically inactive, made almost everyone to regard Kogl s auxin work as a typical scientific fraud. 

Buffel in Belgium, however, published in 1985 a paper re-examining Kogl s reported data, and questioned the authenticity of the samples analysed by Vliegenthart. Buffel suggested some sample exchange 

Three years after the publication of Buffel s paper, Matsui el al. announced the synthesis of F as a mixture of all of its possible stereoisomers, and found it to be biologically inactive. Thus, neither Matsui s 1966 synthesis of E nor his 1988 synthesis of F, both as stereoisomeric mixtures, yielded evidence to support the existence of auxin-b as a plant-growth promoter. We should, however, be careful enough to think about the possible effect of the wrong stereoisomers in the synthetic E and F. In pheromone perception, as we discussed in Chapter 4, there are some cases in which the opposite enantiomer of the natural pheromone strongly inhibits the bioactivity of the correct enantiomer. Especially in the case of 

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