Mosquito, oviposition pheromone

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

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. 

As depicted in Scheme 7, the synthesis of the mosquito oviposition pheromone (-)-6-acetoxy-5-hexadecanolide (28) via an intermolecular aldol reaction represents a powerful demonstration of the high potential of asymmetric enamine catalysis (45, 46). It is noteworthy that a methodologically different successful organocatalytic approach towards 28, based on an asymmetric a-oxygenation, was reported recently (727). Reaction of aldehyde 136 with dibenzoyl peroxide (BzOOBz) and hydroqui-none (HQ) (722) in the presence of the TMS-protected prolinol catalyst (S)-138 followed by a direct allyation gave the benzoyl-protected 139 in moderate yield and good selectivity. Intermediate 139 could then be further transformed to give (—)-(57 ,65)-6-acetoxy-5-hexadecanolide (28) (Scheme 33). 

This hetero-Diels-Alder step marks the first catalytic enantioselective preparation of a C-chiral aUylboronate (i.e., 97). Key to this process is that the possible self-aUylbo-ration between 95 and 97 is avoided by the higher temperature required in the allylb-oration step. An application of this three-component reaction to the synthesis of a mosquito oviposition pheromone was also described. 

A review of syntheses of the Prelog-Djerassi lactonic acid includes carbohydrate-based routes,27 and there have been two further reports of syntheses of the P-hydroxy-5-lactone unit (38) of mevinic acid and its congeners.28, 29 jn a synthesis of the mosquito oviposition pheromone (39), the chiral centres were derived from those of 2,3-0-ethylidene-D-erythrose, with this chiron being extended by Wittig reactions, in a similar manner to the use of 2-deoxy-D-ribose in an earlier approach to the same target (S.-K. Kang and I.-H. Cho, Tetrahedron Lett., 1989, 30, 743). 

Scheme 41 summarizes Couladouros s synthesis of the oviposition attractant pheromone of the Southern house mosquito (Culexpipiensfatigans)y (5R,6S)-6-acetoxy-5-hexadecanolide (28) [66]. The key-steps are (i) -selective Schlosser olefination (A B), asymmetric dihydroxylation (B C), and lactonization of carbonate C to the desired 6-lactone with inversion at C-5. 

Based on the previous work of this group on the three-component aza[4+2]/ allylboration strategy to construct polysubstituted piperidines [62], Gao and Hall developed a catalytic enantioselective version [63] of the corresponding oxygeneous process to construct a-hydroxyalkylated pyrans from 3-boronoacrolein [64], This recent variant of a Vaultier-Lallemand one-pot three-component reaction (see Scheme 12.14) was successfully applied to a concise total synthesis of (5R,6S)-6-acetoxy-5-hexadecanolide 128 (Scheme 12.20), the oviposition attractant pheromone of the female Culex mosquito [65] capable of transmitting the West Nile virus. 

An egg parasitoid uses the sex pheromone of the tussock moth to find the eggs, which are deposited shortly after mating.168 An oviposition attractant for the mosquito, Culexpipiens fatigans, is shown (11.38).169... 

The enantiospecific synthesis of ( + )-ef7r/zro-(5 S, 6i )-6-acetoxy-5-hexadecanolide (475), an optically active form of the major component of an oviposition attractant pheromone of the mosquito Culexpipiens fatigans, exploits the 6,8-dioxabicyclo[3.2.1]octane system to provide... 

A methodologically similar approach was successfully utilized independently for the synthesis of the oviposition attractant pheromone of the female Culex mosquito (—)-(5/ ,6S )-6-acetoxyhexadecanolide (28), by Kotsuki et al. 45) and Li et al. 46). While the Li group carried out a direct aldol reaction between undecanal (23) and cyclopentanone (24) to obtain the desired isomer 25 in excellent enantio- and diastereoselectivity, the Kotsuki group introduced the stereogenic centers by a reaction between 24 and the dithiane 26 under solvent-free conditions (Scheme 7). 

Turning to detritivores, several species of Culex and Aedes mosquitoes are attracted to potential oviposition sites or stimulated to oviposit by pheromones emitted by conspecific eggs, larvae, or pupae (Mulla, 1979). Presumably such pheromones indicate locales of comparatively ample resources which have proved favorable to recent development of conspecifics. On the other hand, larvae of some of these same species, when overcrowded, emit chemicals which are toxic or growth-retarding to conspecifics (Mulla, 1979). How these two facets of chemical regulation of mosquito egg and larval density relate to one another and to individual fitness is uncertain and merits further study. 

Of the simpler 8-lactone natural products, syntheses of malyngolide, mevalonolactone, and an oviposition-attractant pheromone of a mosquito ... 

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