Pheromone asymmetric synthesis

Asymmetric synthesis of spiroketahc pheromones Is also reported. In which the asymmetric redncdon of carbonyl group Is carried out with baker s yeast fScheme 4.22. ... 

Both chiral lactones and ketones have been utilized in asymmetric synthesis of bioactive compounds like lipoic acid [175[ and natural products like various insect pheromones [176[. 

Figure 10.33 Complementary, backbone-inverting approaches for the asymmetric synthesis of the insect pheromone (-l-)-exo-brevicomin.

Asymmetric synthesis of spiroketalic pheromones is also reported, in which the asymmetric reduction of carbonyl group is carried out with baker s yeast (Scheme 4.22).160... 

Scheme 7 summarizes the synthesis of (7JR,llS)-7,ll-dimethylheptadecane (1), the female sex pheromone of the spring hemlock looper (Lambdina athasaria) by Mori [ 18]. Enantiopure alkanes are usually synthesized by coupling enantio-pure building blocks derived from natural products or compounds prepared by asymmetric synthesis. Even among hydrocarbons, chirality is very important for pheromone activity, and in this particular case meso-1 was bioactive, while neither (7R,11R)-1 nor (7S,11S)-1 showed bio activity. 

Synthesis of (—)-(5i , 6S)-6-acetoxyhexadecanolide, a mosquito oviposition pheromone of Culexpipiens fatigans, was also prepared by asymmetric synthesis. 

In an elegant asymmetric synthesis of natural serricornin (148) by Mori et al.164), an overall enantioselective alkylation of diethyl ketone via its SAMP-hydrazone (144) was again the key step. (148) is the sex pheromone of the female cigarette beetle,... 

Van Summeren, R.P., Reijmer, S.J.W., Feringa, B.A. andMinnard, A.J. (2005). Catalytic asymmetric synthesis of enantiopure isoprenoid building blocks application in the synthesis of apple leafminer pheromones. Chem. Comm., 2005, 1387-1389. 

There Is more on asymmetric synthesis, including sortie pheromone examples,... 

Asymmetric syntheses directed toward construction of enantiomers of the western and southern corn root-worm pheromones are described. A brief review of the subject of asymmetric synthesis as it is related to the synthesis of insect sex pheromones is presented. The laboratory s previous research with chiral pheromones is summarized (Japanese beetle, white peach scale, and lesser tea tortrix) before detailing synthetic work on the pheromones of the aforementioned rootworm species. Throughout the course of the synthetic effort, cholesteric stationary phases for GLC have found use. Their superior ability to separate crucial diastereomeric intermediates for synthesis is detailed. 

Stereochemistry and asymmetric synthesis are topics with which chemists traditionally have been concerned (1 ). In recent years there has been a virtual explosion of literature in the area of asymmetric organic synthesis that has fortuitously paralleled the increased awareness of insect pheromone stereochemistry. Many useful reviews of asymmetric synthesis exist (2, 2> 4, 5, 0 and this paper will only briefly direct the reader s attention to examples of reported syntheses by type that may be of potential general use for pheromone synthesis. It should be clear even to the casual reader that this field is in need of almost annual review and current literature would have to be consulted in the face of an original problem in synthesis. 

THTs are well known to undergo desulfurization with Raney-Ni. Recently this has been used in the asymmetric synthesis of the sex pheromones oiMacrodiprion nemoralis (Scheme 42) <2000S1863>. 

The practice and theory of enantioselective CGC was comprehensively reviewed. Racemic oxygen-, nitrogen- and sulfur-containing selectands can be separated without prior derivatization into enantiomers by CGC on optically active metal(II) bis[3-(perfluoro-acyl)-(lR)-camphorate] (61) selectors. Peak inversion is obtained when the selectors with opposite configuration are employed. Applications pertain to chiral analysis in asymmetric synthesis, enzymatic reactions, pheromone and flavor chemistry. ... 

There is more on asymmetric synthesis, including some pheromone examples. In Chapter 45. The protecting groups used In this synthesis were covered in Chapter 24, and aza.enolate alkylations in Chapter 26. 

The natural product (R)-sulcatol is a male-produced aggregation pheromone of the ambrosia beetle. This insect can devastate entire forests when its population is out of control.Various studies revealed that different species respond to the compound in different enantiomeric excess. The asymmetric synthesis of (R)-sulcatol was accomplished in the laboratory of S.G. Davies using a stereospecific [2,3]-Meisenheimer rearrangement as the key step. The treatment of the allylic amine substrate with mCPBA followed by the filtration of the reaction mixture through deactivated basic alumina afforded the desired hydroxylamine as a single diastereomer. 

Enders, D., Eichenauer, H. Asymmetric synthesis of ant alarm pheromones - a-alkylation of acyclic ketones with practically complete asymmetric induction. Arrgew. Chem. Int. Ed. Engl. 1979,18, 397. 

Couladouros, E. A., Mihou, A. P. A general synthetic route towards y- and 5-lactones Total asymmetric synthesis of (-)-muricatacin and the mosquito oviposition pheromone (5R,6S)-6-acetoxy-hexadecanolide. Tetrahedron Lett. 1999, 40,4861-4862. 

There are three methods available for the enantioselective synthesis of pheromones (1) derivation from enantiopure natural products, (2) enantiomer separation (optical resolution), and (3) chemical or biochemical asymmetric synthesis. Practitioners of enantioselective synthesis must be familiar with the analytical methods for the determination of enantiomeric purity of an optically active compound. These basic methods will be explained briefly in this section, and discussed in depth through examples in the later sections of this chapter. 

Figure 4.13 Asymmetric synthesis of the pheromone of Eysarcoris lewisi...

Helmchen has used this methodology in asymmetric synthesis of the three stereoisomers of the tsetse fly pheromone [73] and the side chain of a-tocopherol... 

After reading Silent Spring , I became interested in insect pheromones, because its application may provide us with a new and environmentally benign method of pest control. 1 was also interested in the evolving field of asymmetric synthesis. Accordingly, 1 started my enantioselective pheromone synthesis in 1973. The first work was the determination of the absolute configuration of the dermestid beetle pheromone [18]. By synthesizing the (S)-(+)-enantiomer of the pheromone from... 

Alkylation of lithiated hydrazones forms the basis of an efficient method for the asymmetric alkylation of aldehydes and ketones, using the optically active hydrazines (5)-l-amino-2-(methoxymethyl)pyrroUdine (SAMP) 59 and its enantiomer (RAMP) as chiral auxiliaries. Deprotonation of the optically active hydra-zones, alkylation and removal of the chiral auxiliary under mild conditions (ozonol-ysis or acid hydrolysis of the A-methyl salt) gives the alkylated aldehyde or ketone with, generally, greater than 95% optical purity. This procedure has been exploited in the asymmetric synthesis of several natural products. Thus, (S)-4-methyl-3-heptanone, the principal alarm pheromone of the leaf-cutting ant Am texana, was prepared from 3-pentanone in very high optical purity as shown in Scheme 1.74. 

In contrast, Michael additions of a,a-disubstituted lithium enolates proceed, apparently via the chelated form of enone sulfoxides (Figure 5.2), with almost complete jt-facial diastereoselectivity [104]. This methodology has been used in the asymmetric synthesis of the pheromone, (-)-methyl jasmonate (121), from cyclopentenone sulfoxide (98b) [105] via the intermediate (120), which was formed in at least 98% enantiomeric purity upon asymmetric Michael addition of bis a-silylated a-lithioacetate to (98b). Addition of the a-bromo enolate (122) to enantiomerically pure (98a) and oxidation gives the product sulfone (123), with almost complete asymmetric -induction with respect to the sulfoxide. Sulfone (123) was then converted into the steroidal sex hormone, (+)-oestradiol (124) (Scheme 5.42) [106]. 

Photochemical cycloadditions have been among the least widely studied cycloaddition reactions of carbohydrate derivatives, however, some noteworthy examples have been described in the earlier as well as more recent lierature.. Photoannulations of pyranoid enones with both vinyl acetate and ethylene have been described by Fraser-Reid, Hicks, and Primeau 49). Cycloaddition of vinyl acetate to 86 gave the cyclobutano pyranoside 87 as a mixture of diastereomers. This reaction was explored as an approach to the asymmetric synthesis of the insect pheromone grandisol. 

This is an unconventional way to optimize the efficiency of an asymmetric synthesis. This prediction has not yet bwn verified experimentally however, it finds analogy in the optimal biological activity which is not always related to 100% ee for the drug or the compound (eg some insect pheromones). This arises from a multi-sites biological... 

Research interests include synthetic organic chemistry, especially asymmetric synthesis and the use of enzymes in organic synthesis, with special reference to biologically active compounds such as insect pheromones and related chemical signals natural products chemistry wood chemistry. 

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