Xiongwei Shi

Male-released sex pheromone of the stink bug Piezodorus hybneri

Male-released semiochemicals of the stink bug Piezodorus hybneri (Heteroptera: Pentatomidae) elicit attraction of male and female bugs and homosexual behavior in males. Three active components were isolated from the airborne volatiles of males by flash chromatography, with the activity monitored by GC-EAD and behavioral bioassay. The pheromone system was characterized as a mixture of β-sesquiphellandrene, (R)-15-hexadecanolide, and methyl 8-(Z)-hexadecenoate (ratio: 10:4:1), and the activity of the semiochemicals was assessed with authentic samples. Enantiomerically pure samples of the R and S macrolactones were obtained by Yamaguchis and Mitsunobus macrolactonization of a key intermediate, (R)-15-hydroxyhexadecanoic acid. The nonnatural S stereoisomer was neither a beneficial nor a behavioral antagonist. Individual constituents or binary mixtures were active, but the optimal male response was elicited only by the full mixture. Behavioral observation and the fact that the onset of pheromone production is coincident with ovarian development strongly suggest that these semiochemicals are, in fact, sex pheromones.

A new synthesis of alkylated 2H-pyran-2-ones and its application to the determination of the relative and absolute configuration of supellapyrone, sex pheromone of the brownbanded cockroach, Supella longipalpa

Abstract The sex pheromone of the brownbanded cockroach, Supella longipalpa, can be synthesized by direct coupling of a brominated pyrone with an alkylzinc reagent. The stereochemistry of the natural pheromone has been assigned as (2′R, 4′R)-5-(2′,4′-dimethylheptanyl)-3-methyl-2H-pyran-2-one by a combination of synthesis, chiral gas chromatography, and electrophysiological measurement.

Spirocyclic Defensive Alkaloid from a Coccinellid Beetle

Abstract A new alkaloid, chilocorine B, was characterized from a coccinellid beetle, Chilocorus cacti. This compound represents the first spirocyclic example of the new “dimeric” alkaloid family whose structures are derived from two thirteen-carbon tricyclic subunits, 2-methylperhydro-9b-azaphenalene and 3,4-dimethyloctahydro-8bazaacenaphthylene.

Assignment of absolute stereochemistry to an insect pheromone by chiral amplification

Chiral amplification, a new strategy for determining the absolute configuration of difficulty available natural secondary alcohols or analogous amines, is described. Using this technique, the R configuration can be assigned to both components of the male sex pheromone emitted by the longhorn beetle, Anaglyptus subfasciatus. The application of this approach to fourteen alcohols and four amines illustrates its scope and limitations.

Synthesis and absolute configuration of 2-(12′-aminotridecyl)-pyrrolidine, a defensive alkaloid from the Mexican bean beetle, Epilachna varivestis

Abstract The synthesis of 2-(12′-aminotridecyl)-pyrrolidine ( 1 ), a defensive alkaloid recently isolated from the Mexican bean beetle, Epilachna varivestis , is described. The (2 S ,12′ R ) configuration is assigned to this alkaloid by comparing the 1 H NMR spectrum of its ( S )-MTPA derivative with that of ( R )- and ( S )-MTPA [α-methoxy-α-(trifluoromethyl)phenylacetyl] derivatives of the synthetic sample. These results suggest that the seventeen carbon skeleton of 1 is acetate rather than proline derived.

Synthesis and the determination of the absolute configuration of matsuone, sex pheromone of female Matsucoccus pine scales

Abstract The four possible optical isomers of matsuone ( 1 ), female sex pheromone of Matsucoccus resinosae pine scales, were convergently synthesized in high optical purities. The absolute configuration of the natural product has been assigned as (2 E , 4 E , 6 R , 10 R )-4,6,10,12-tetramethyltridecan-2,4-dien-7-one. Bioassays with M. resinosae using these stereoisomers reveal that the unnatural (6 R , 10 S )-isomer mimics the natural pheromone.

SYNTHESIS AND ABSOLUTE CONFIGURATION OF TWO DEFENSIVE ALKALOIDS FROM THE MEXICAN BEAN BEETLE, EPILACHNA VARIVESTIS

Abstract Syntheses of (2 S ,12′ R )-2-(12′-aminotridecyl)-pyrrolidine ( 1 ) and (2 S ,12′ R )-1-(2″-hydroxyethyl)-2-(12′-aminotridecyl)-pyrrolidine ( 2 ), two defensive alkaloids recently isolated from the Mexican bean beetle, Epilachna varivestis , are described. By a comparison of 1 H NMR data of MTPA derivatives of natural alkaloid 2 with those of the synthetic standard, we confirm the (2 S ,12′ R ) configuration previously suggested for this alkaloid. Further support of these assignments was provided by the synthesis and 1 H NMR investigation of (2 S ,12′ S )- 1 , (2 S ,12′ S )- 2 , and their MTPA derivatives.