Synthesis and field testing of esters of (2 R )-butan-2-ol and (2 S )-butan-2-ol and monounsaturated fatty acids as sex attractants for the males of Procridinae species (Lepidoptera: Zygaenidae)

In the family Zygaenidae (Lepidoptera) with more than 1000 species a complete chemical analysis of the structure of female sex pheromones has been carried out for only three species of the subfamily Procridinae while sex attractants have been found for males of more than 60 species of two subfamilies: Procridinae and Zygaeninae. The synthesis of new sex attractants was performed from ( Z )-dodec-5-enoic acid and R - and S -enantiomers of butan-2-ol at the Crimean Federal University in 2021. The biological activity of received esters was tested during fieldwork in the Crimean Peninsula. It has been proved that (2 R )-butan-2-yl ( Z )-dodec-5-enoate (named EFETOV-S-5) and (2 S )-butan-2-yl ( Z )-dodec-5-enoate (named EFETOV-S-S-5) are sex attractants for the males of Jordanita ( Tremewania ) notata (Zeller, 1847), while (2 S )-butan-2-yl ( Z )-dodec-5-enoate (EFETOV-S-S-5) is a sex attractant for Adscita ( Adscita ) geryon (Hübner, 1813). In addition, (2 R )-butan-2-yl ( Z )-hexadec-9-enoate and (2 S )-butan-2-yl ( Z )-hexadec-9-enoate were synthesised in 2022. However, these esters did not attract any of the Zygaenidae species which are common in the Crimea.

1. Synthesis of (Z)-dodec-5-enoyl chloride. 5 g (0.025 mol) of (Z)-dodec-5-enoic acid was placed in a 50 ml round-bottom flask equipped with a water-cooled reflux condenser. 10 ml of anhydrous benzene, 0.5 ml of N,N-dimethylformamide and 2.2 ml (0.03 mol) of thionyl dichloride were added. The reaction mass was heated to boiling and maintained at boiling point for one hour. At the end of the reaction, the solvent (benzene) and excess of thionyl dichloride were removed under vacuum on a rotary evaporator. Acyl chloride was used at the stage of synthesis of the corresponding ester.
As a positive control, we used rubber caps impregnated with 50 µl of the sex attractant EFETOV-2 (the racemic mixture of (2R)-butan-2-yl dodec-2-enoate and (2S)-butan-2-yl dodec-2-enoate), which had been synthesised earlier according to the procedure published by Efetov et al. (2014c). The efficacy of baits with EFETOV-2 has been proven for seven species of Zygaenidae of the Crimean fauna . Empty rubber caps without any synthetic compounds were used as a negative control.
The lures with labelled cardboard holders were fixed in transparent plastic Delta traps containing removable sticky layers (Figure 3).

FIELD EXPERIMENTS
Attempts to observe the attraction of males of Zygaenidae species to synthetic esters were conducted in 2021 (with EFETOV-S-5 and EFETOV-S-S-5) and 2022 (with EFETOV-S-9-16 and EFETOV-S-S-9-16) at four localities of the Crimean Peninsula in biotopes corresponding to the preferred habitats of the target species (Efetov, 2005). The experimental and control traps were hung on bushes or trees at a height of 1.0-1.5 m above the ground. The distance between different types of traps was at least 10 meters. The traps were inspected on average once a week. Sometimes we just put the baits on rocks on the ground (the distance between the baits was not less than several meters). In this case, we collected attracted moths by catching them with a net near the rubber caps. All
It should be noted that 44 males of Th. ampellophaga were found in sticky traps with sex attractant EFETOV-2, that was used as a positive control in 2021-2022 in locality 4. However, the males of this species were absent in traps with newly synthesized esters. Besides this, some other Zygaenidae species (observed in the biotopes on the wing) did not respond to the tested baits. In our fieldwork, A. geryon were attracted to the S-enantiomer of 2-butan-2-yl dodec-5-enoate. This is in good agreement with the data which have been obtained earlier in Bulgaria, Crimea, Hungary and Italy (Efetov et al. 2015b;Subchev et al. 2010), where males of this species were mainly attracted to the S-enantiomer of 2-butan-2-yl dodec-7-enoate alone or in a mixture with the corresponding R-enantiomer. In the case of (2R)-butan-2-yl dodec-7-enoate and (2S)-butan-2-yl dodec-7-enoate, the presence of the R-enantiomer does not influence the attractiveness of the Senantiomer. The males of A. geryon were not found in sticky traps with the racemic mixture of 2butan-2-yl dodec-2-enoate and its enantiomers alone. The males only flew up at a close distance of about 20-50 cm to the rubber caps with EFETOV-2 and then flew away. The main catches of this species in field trials with the enantiomers of 2-butan-2-yl dodec-5-enoate and 2-butan-2-yl dodec-7enoate were recorded in sticky traps.
The main catches of J. notata were recorded in traps baited with (2R)-butan-2-yl dodec-2-enoate, (2R)-butan-2-yl dodec-5-enoate, (2R)-butan-2-yl dodec-7-enoate or in traps with lures containing these compounds in mixtures with other substances (Efetov et al. 2015bRazov et al. 2017;Subchev et al. 2010). The presence of the corresponding Senantiomers does not inhibit the attractiveness of the R-enantiomers for J. notata. It is clear that the stereoisomerism of the ester molecules is more important for their recognition by the olfactory receptors of males of this species than the position of the double bond in acid radicals.