Determination of enantiomer composition of several bicyclic ketal insect pheromone components

Semiochemicals in the Natural History of Southern Pine Beetle Dendroctonus frontalis Zimmermann and Their Role in Pest Management

“…Dendroctonus frontalis has been reported to produce predominantly the minus enantiomer of frontalin: 85% for an unstated collection site (Stewart et al, 1977); 95% in Mississippi, United States (Sullivan et al, 2007b), and 94% in Chiapas, Mexico (Niño-Domínguez et al, 2015b). Compositions of 25-35% of the (À)-enantiomer were reported for beetles from South Carolina, North Carolina, and Texas, United States (Grosman et al, 1997), although this study had methodological problems (discussed below).…”

Insect Pheromones: A Critical Review of Recent Advances in Their Chemistry, Biology, and Application

“…Males of D. frontalis in a pedestrian type bioassay, are more responsive to ( -)-frontalin than to (+ )-frontalin, while females are not responsive to either enantiomer (321). The natural ratio of the frontalin enantiomers in D. frontalis females is 85 ( -) : 15 ( +) (46) . Data on field tests using optically pure isomers of brevicomin, frontalin and ipsenol indicate that activity is associated with only one enantiomer of each compound (322).…”

“…In some cases, this problem can be alleviated by use oflanthanide shift reagents such as Eu(fod)3 (45). Chiral shift reagents have been used to determine the enantiomeric composition of several pheromone bicyclic ketals (150, 195, 303a) (46) and alcohols (1, 229, 232, 266a, 294a) (45) (see Chart I). The cx-methoxy-cx-trifluoromethylphenylacetyl derivatives of these alcohols were also used to determine enantiomeric composition (45,47,48).…”

“…MORl synthesized the enantiomers of frontalin (133, Scheme 43) and exobrevicomin (122, Scheme 34); STEWART et al (46) established that the natural enantiomers were (IS,5R)-( -)-frontalin (195) in males and (320) claim that these two enantiomers are the most active forms of these compounds. Males of D. frontalis in a pedestrian type bioassay, are more responsive to ( -)-frontalin than to (+ )-frontalin, while females are not responsive to either enantiomer (321).…”

Novel diffusion-dilution method for release of semiochemicals: Testing pheromone component ratios on western pine beetle

“…Tilden and Bedard (1985) have used these component ratios to test three release rates over two orders of magnitude (1 x, 10 x, and 100 x) compared to similar levels of a 1 : 1 : 1 (E : F : M) ratio. Their release rates of the active enantiomers of the 1 : 1 : 1 mixture at the 1 x level began at amounts equivalent to that released by 52 females and 220 males according to calculations based on the results of Browne et al (1979), assuming beetles release pure enantiomers (Stewart et al, 1977). The highest level (100 x) was equivalent to 5200 females and 25,000 males.…”