Carpenter bees

An enantio-selective enzymatic hydrolysis of meso( )-2,5-diacetoxy-3-hexene gives (+)-( )-(25 ,5/ )-5-acetoxy-3-hexen-2-ol in 77% yield (92% ee).97 The monoacetate with its two allylic groups offers possibilities for stereo-controlled introduction of nucleophiles via Pd(0) catalysis. Synthesis of both enantiomers of the Carpenter bee pheromone based on this strategy is presented in Scheme 5.14.98... 

The diacetoxylation works well with a number of cyclic and acyclic conjugated dienes and has been applied to the synthesis of natural products33,34. For example, the meso diacetate from 2,4-hexadiene was used for the enantiodivergent synthesis of the carpenter bee pheromone343. 

Barthell, J. F. and Knops, J. M. H. (1997). Visitation of evening primrose by carpenter bees evidence of a mixed pollination syndrome. Southwestern Naturalist 42 86-93. 

Males of the carpenter bee, Xylocopa hirutissima, establish and defend territories that are located proximate to projecting trees on mountain tops (146). These territories are maintained by a mandibular gland secretion that contains, as a major constituent, the cis-lactone of 2-methyl-5-hydroxyhexanoic acid (XXXVIII) (147). 

Additional examples where chloroacetates from acyclic dienes have been used include the synthesis of pentadienylamines [96], dienesulfones [97], c-methylenecyclopentenones [98], marine natural products [99], and the carpenter bee pheromone [82]. Some additional Synthetic applications of the chloroacetoxylation of cyclic dienes are given in Refs. [100-104]. Chloroacetoxylation was also used to prepare a number of starting materials for the intramolecular reactions discussed in this chapter. 

Reaction of 147 with the mixed cuprate of 3-methy 1-2-butene gives, in one step, (/ )-( — )-sulcatol (148) the enantiomer of an aggregation pheromone of a wood-boring ambrosia beetle [53]. Oxirane 147 has also been instrumental in the synthesis of (2S, 5/ )-2-methyl-5-hex-anolide (151), one of the antipodes of the sex pheromone of the carpenter bee [54] (Scheme 22) and the macrolide fungal metabolite (7 )-recifeiolide (155) [55] (Scheme 23). 

The reagent was used to resolve 5-cyanopentane-2-ol (1), a precursor to the four possible isomeric lactones (3). One of the cis-enantiomers is the carpenter bee pheromone. ... 

Delphinidin (2) and its derivatives are found frequently in bee-pollinated plants and are typical of families such as the Boraginaceae, Hydrophyllaceae, Polemoniaceae, and Scrophulariaceae. Sometimes the color of flowers of a species apparently varies in response to the type of pollinator present. As an example, one species of Penstemon, a blue, carpenter bee-pollinated species, hybridizes naturally with a red, hummingbird-pollinated species to produce a purple-flowered hybrid. Although normally this hybrid would fall outside the limits that the pollinators of the parental species would pollinate, this purple flowered hybrid is, fortuitously, pollinated by a wasp (Harbome, 1988c). 

Alkyl 2-acyloxy-3-deoxy-D-eryt7zr o-hex-2-enopyranoside diesters (91) have been converted into chiral 5-hydroxy-2-methylhexanoic acid lactones which constituted the pheromone of the Carpenter bee. Treatment of (90) with boron trifluoride etherate gave (91), which on addition of methylenetriphenylphosphorane gave a most interesting transformation to (92). A further reaction sequence... 

The chemistry of Dufour s glands in Nomada, the only nomadine genus investigated, is discussed in Section 14.7. In the Xylocopinae, saturated and unsaturated hydrocarbons dominate the Dufour s gland extracts of the large carpenter bee, Xylocopa virginica (Vinson et al., 1978), which also contains methyl esters of fatty acids. 

Velthuis, H. H. W. and Camargo, J. M. F. de (1975) Further observations on the function of male territories in the carpenter bee Xylocopa Neoxylocopa) hirsutissima Maidl (Anthophoridae, Hymenoptera). Neth. J. Zool., 25, 516-28. 

Chemistry of mandibular gland secretions of small carpenter bees (Ceratina spp.) Ann, ent, Soc, Am., 70, 635-6. 

Meso diacetates obtained from 1,4-diacetoxylation of conjugated dienes have been used for enzyme-catalyzed hydrolysis in enantioselective transformations [79-85]. In an application toward the carpenter bee pheromone (Scheme 11.18) [79], the meso-diacetate 54, obtained from stereoselective 1,4-diacetoxylation of (B,Z)-2,4-hexadiene, was enzymatically hydrolyzed to hydroxyacetate 55 with 92%... 

Enantiomerically pure lactonic pheromones 607-611, of the carpenter bee, blacktailed deer, Japanese beetle, rove beetle, and Oriental hornet, respectively, have been synthesized from racemic cyano alcohols of type 612. The key to the success of the overall approach is the facile separation of diastereomeric carbamates derived from cyano alcohols of type 612 by automated multigram LC. The chosen approach also facilitates the assignment of absolute configurations to the lactone enantiomers and their precursors. In the case of 607, direct determination of enantiomeric purity and absolute configuration is also possible using the chiral solvating agent 2,2,2-trifluoro-l-(9-anthryl)ethanol [439]. 

A further significant example is the stereospecific synthesis of (/ , 5 )-5-hydroxy-2-methylhexanoic acid lactone (the major component of the Carpenter bee pheromone) [5 c]. 

Similarly, Ohveira et al. have reported the synthesis of all four possible dia-stereomers of a component of the pheromone blend of the carpenter bee Xylocopa hirutissima via alkylation of 4,4-dimethyl-2-oxazoline derivatives [61] (Scheme 23). In this case, the carboxylic acid, allowing the formation of the 5-lactone, is masked as an oxazoline. The reaction of the anion of 2-ethyl-4,4-dimethyl-2-oxazoline 120 with iodide 121 gave compound 122 in 92 % yield, which was hydrolyzed and cyclized in one-pot under acidic conditions to provide a mixture of stereoisomers 123 and 124. 

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