Stegobinone

The pheromone produced by females of the drugstore beetle was the first to be identified in an anobiid beetle 2,3-dihydro-2,3,5-trimethyl-6-(r-methyl-2 -oxobutyl)-4ff-pyran-4-one (stegobinone) [256] which by independent synthesis [257] was shown to keep (2S,3R,1 R)-configuration 123. A second compound... 

A chiral synthesis of stegobinone (SSS) is based on the cleavage of (25,35)-2,3-epoxybutane with lithium diphenylcuprate, which occurs with complete inversion. The resulting chiral alcohol is converted into the mixed anhydride, which is used to acylate the... 

Figure 6.6 Structures of 2,3-dihydro-2,3,5-trimethyl-6-(1 -methyl-2 -oxobutyl)-4H-pyran-4-one (stegobinone), pheromone of Stegobium paniceum (L.) (Anobiidae) (Kuwahara et al., 1978) and (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6,8-decatetraene, pheromone component of Carpophilus hemipterus (L.) (Nitidulidae) (Bartelt et al., 1991). The carbon skeletons are identical, and likely derived through similar pathways (see text).

Drugstore beetle (Stegobium paniceum) is a serious pest of a wide variety of commodities and stored products. In 1978 Y. Kuwahara et al. proposed the structure of stegobinone, the major and crystalline component of the female-produced sex pheromone of 5. paniceum, as 114 (Figure 4.69). Nothing was... 

In 1979, we reported a biomimetic synthesis of (2S, 3f , l/R S, )-114 in a low yield (5.6%) as a racemic and diastereomeric mixture.120,121 Although the synthetic product was pheromonally active, its activity was shown at a dosage of about 10 4pg, while the natural stegobinone was active at 3 x 10—7 jxg. This fact indicated that the synthetic (25, 3/ , l,/ 5 )-114 contained a certain inhibitory stereoisomer. It took about 20 years to solve this problem completely. We published our preliminary results of this synthesis in Tetrahedron Letters,120 I was surprised in the following week to see the next issue of the same journal, which contained a paper by Professor A. Hassner reporting the same biomimetic synthesis of 114.122 Quite often the same idea occurs to the minds of different people. 

Our first synthesis of the natural (2S,3R,VR)- 4 was published in 1986.124 As shown in Figure 4.71, the required building block B was prepared from ethyl (,R)-3-hydroxybutanoate of 100% ee via A. Another building block C was synthesized from methyl (,R)-3-hydroxy-2-methylpropanoate (97% ee). Esterification of B with C gave the key intermediate D, whose intramolecular cyclization afforded the required pyra-none system. The synthetic (2S,3R,VR)- 4 showed spectral properties identical to those of the natural stegobinone, although it remained as an oil due to the contamination with trace amounts of impurities. Our... 

Figure 4.70 Synthesis of (2S,3R, VRS)-stegobinone. Modified by permission of Shokabo Publishing Co., Ltd...

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