Positions and Stereochemistry of Methyl Branches in the Novel Sex Pheromone Components Produced by a Lichen Moth, Lyclene dharma dharma

Abstract

Female moths of Lyclene dharma dharma (Arctiidae, Lithosiinae) produce three sex pheromone components (I-III), for which we assigned the following novel chemical structures; 6-methyl-2-octadecanone (1) for I, 14-methyl-2-octadecanone (2) for II, and 6,14-dimethyl-2-octadecanone (3) for III. In the Iriomote Islands where the insects were collected, a lure including racemic 1 and 2 attracted the male moths without mixing 3. In this study for further confirmation of the plane structures, the positional isomers with a methyl branch at the 4-, 5-, 7-, 13-, or 15-position (4-8, respectively) were synthesized. The GC-MS analyses revealed that natural components I and II were best fitted with those of 1 and 2, respectively, among the methyl-2-octadecanones examined, indicating the usefulness of this analytical instrument and authentic standards for the determination of the positions of methyl branches. In field trapping tests, 4-8 could not substitute for 1 or 2, nor did these compounds inhibit the active binary lure of 1 and 2, indicating that the males strictly recognized the 2-ketones with a methyl branch at the 6- or 14-positions. Next, the absolute configurations of I and II were determined by HPLC with a normal-phased chiral column (Chiralpak AD-H), which could separate the enantiomers of both 1 and 2. The chiral HPLC analysis of a crude pheromone extract indicated that the females exclusively produced (S)-1 and (S)-2. Furthermore, a field evaluation of each enantiomer revealed that (S)-1 and (S)-2 were bioactive but (R)-1 and (R)-2 were not.

Semiochemicals containing lepidopteran sex pheromones: Wonderland for a natural product chemist

“…(14), fused-ring comp. (68), and heterocyclic comp. (16) for the terpenes (total 275); hydrocarbons (49), primary alcohols and derivatives (28), secondary alcohols and esters (31), ketones Fig.…”

Chiral methyl-branched pheromones

“…The spectral analysis of several synthetic branched 2-ketones indicated that the 6-methyl-2-ketone with characteristic ions at m/z 113 and 95 (113 À H 2 O) was differentiated from the 4-, 5-, and 7-methyl-2-ketones, but differentiation of the mass spectra of the 13-, 14-, and 15-methyl-2-ketones was difficult. 236 A structural determination of the 3,13-dimethyl pheromone (97) was also conducted using a mass-spectral analysis of the pheromone derivative and some synthetic candidates. 286 By transesterication with KOH in MeOH, the novel ester was converted into the methyl ester (97 0 ), which showed ions at m/z 101 (base peak) and 74, indicating a 3-methyl structure (Fig.…”

Enantioselective Synthesis of the Sex Pheromone of Lichen Moth, Miltochrista calamine, and Its Diastereomer

“…5 The adults of Lithosiinae are called lichen moths because their larvae mainly feed on lichens. 6,7 Lichen moths are found throughout the world and contribute to the ecosystem of the forest. 8,9 In 2010, the sex pheromone of Miltochrista calamine was identified as (5R,7R)-5-methylheptadecan-7-ol (1a, Figure 1).…”