A-multistriatin

Blight M. M., Wadhams L. J. and Wenham M. J. (1978) Volatiles associated with unmated Scolytus scolytus beetles on English elm differential production of a-multistriatin and 4-methyl-3-heptanol, and their activities in a laboratory bioassay. Insect Biochem. 8, 135-142. 

The use of iodoetherification has been exploited in the synthesis of precursors to mono- and bis-THF acetogenins,234 potent antitumor and pesticides. Also, has been used in the synthesis of tetrahydrofuran analogs of precursors to pseudomonic acid.235 As well, N1S has been used as the iodine source, for example in the synthesis of other acetogenins.236 Other compounds synthesized via iodocyclization include ( )-(a)-multistriatin,237 ( )-velbanamine, and ( )-isovalbanamine,238 and (+)-citreoviral.239... 

Stereoselective hydrogenation. A stereoselective synthesis has been reported of the naturally occurring form of a -multistriatin (5), the aggregation pheromone of the European elm beetle, the vector of Dutch elm disease in North America. The synthesis is another example of the value of carbohydrates as chiral precursors to natural products. In this case, the known epoxide 1, derived from D-glucose, was converted in several steps into 2. The crucial next step required hydrogenation to 3 with the 1,3-diaxial configuration of the two methyl groups. The desired selectivity was attained by use of Wilkinson s catalyst. 

The Sharpless epoxidation has been used to synthesize many chiral natural products, including two insect pheromones—(+)-a-multistriatin and (-)-frontalin, as shown in Figure 12.11. 

As illustrated in Scheme 11.10, enone 32, prepared from D-glucal in a multistep sequence, was reacted with lithium dimethylcuprate. Clean axial attack of the reagent at C4 gave the substituted ketone 33. Subsequent Wittig methylation and reduction was used to introduce the second methyl group of 34, a key intermediate in the synthesis of a-multistriatin. The same sequence was used in the preparation of calcimycin (A23187), the 4-C-methyl synthon 33 being used to construct the two required chirons [50]. 

Application of the preceding strategy to multistriatin synthesis (Scheme 11.26) started with compound 7, which was deoxygenated at C3 and further elaborated to ketone 106 [49]. Wittig methylenation provided 107, and subsequent double bond reduction using Wilkinson s catalyst afforded the dimethylated compound 34 [93]. Further manipulation yielded a-multistriatin 108, the pheromone of Scolytus multistriatus. Other syntheses of this pheromon from sugars have been reported [48,94,95]. 

Lagrange, A, Olesker, A, Costa, S S, Lukacs, G, Tong, T T, A route from D-galactose to the aggregation pheromone component (—)-a-multistriatin, Carbohydr. Res., 110, 159-164, 1982. 

A number of related enol ethers are accepted as substrates by antibody 14D9. For example, enol ether 57 give (S)-ketone 58, which has been used for a stereospecific synthesis of the pheromone (-)-a-multistriatin (Scheme 19) [87]. 

Homogeneous catalysts also proved useful in stereoselective hydrogenation. A crucial step in the total synthesis of the aggregation pheromone a-multistriatin requires hydrogenation to 29 with the 1,3-diaxial configuration of the 2-methyl groups. Selectivity is obtained over RhCl(PPh3)3 ... 

Methyl-3-heptanol is only part of the elm bark beetle pheromone. It is released together with a-multistriatin and a-cubebene. The latter compound is to be regarded as a kairomone released from the tree. The three substances work synergistically (see Silverstein, 1981 and references therein for further details). 

The structure of (-)-a-multistriatin was found to be the structure (15, 2R, 45, 5/i)-(-)-2,4-dimethyl-5-ethyl-6,8-dioxabicyclo-[3.2.1]-octane (24a) (Mori, 1976 Pearce et al., 1976 Cemigliaro and Kocienski, 1977). However, populations of the beetle epidemic to forests in the Upper Rhine Valley did not aggregate in response to (- )-a-multistriatin instead, another of its stereoisomers, (- )-5-multistriatin (24b) exerted attractive action when combined with 23 and 25. 

Descriptions of a variety of routes to a-multistriatin (110) and related compounds have been published. Two reported syntheses of sarracenin... 

---