A convenient total synthesis of
The sex pheromone of ACB, released by adult females, is a mixture of
Chemical structure of the sex pheromone of ACB.
To date, some strategies have been developed for synthesizing the sex pheromone of the ACB. These existing strategies focused on the carbon chain increasing or decreasing to construct the main chain. Based on the carbon chain increasing synthetic strategies [
Comparison between the existing literature synthetic strategies and this work.
In spite of many advantages, the existing synthetic routes have some drawbacks, such as requiring too many steps, lower overall yields, lack of cost-effectiveness, or separate components preparation process, which required subsequent mixing before field application. Therefore, the development of the cost-effective and operationally simple synthetic strategy for the sex pheromone of ACB is still of great interest in agrochemicals.
Herein, we describe a new
As shown in Scheme
Synthesis of the target compounds.
Overall, a convenient synthesis route for the sex pheromone of the
Electroantennogram (EAG) technology, which is based on the discovery by Schneider [
In order to screen the biological activity of the attractiveness of synthetic sex pheromone molecules to ACB male moths, the EAG assays were performed. The results are shown in Figure
Electroantennogram responses [mV ± SE (standard error)] of ACB male moths to binary blends of the ratio 27 : 73
The results showed that there was a relationship between EAG response and dose. At doses ranging from 1 to 1000
The
Generally, the EAG responses of synthetic sex pheromone to ACB male moths were observed. The results showed that the target mixture molecules, where the
All reagents were commercial and used without further purification. Tetrahydrofuran (THF) was freshly distilled from lithium aluminium hydride under a nitrogen atmosphere. Chromatography was carried on flash silica gel (300−400 mesh). All reactions were monitored by TLC, which was performed on precoated aluminium sheets of silica gel 60 (F254). Melting points were uncorrected. The 1H-NMR and 13C-NMR spectra were determined at 25°C at 500 MHz and 125 MHz, respectively, with TMS as an internal standard. All shifts are given in ppm. High-resolution mass spectra (HRMS) were obtained using a Bruker microTOF II focus spectrometer (ESI). Gas chromatographic-mass spectrometric (GC-MS) analysis was conducted using an Agilent 5975 spectrometer. The GC-MS data were obtained using a 30 m × 0.25 mm column of DB-1701 phase. The column temperature was run from 120 to 260°C at 3°C/min and held at 260°C for 5 min using helium as carrier gas. Electron impact (EI) mass spectra were collected at 70 eV with separator and source at 180°C. EAG Systems (Syntech, Dutch) include Syntech IDAC-2 Acquisition Controller and Software, Syntech CS-55 Stimulus Controller Unit, Syntech Pre-Amplifier for Recording from Taste Sensilla, and Syntech MP-15 Micromanipulator.
To a solution of brassylic acid (
Glacial acetic acid (23 mL), water (30 mL), and concentrated sulfuric acid (0.08 mL) were added to a solution of crude
Compound
Potassium tert-butoxide (0.2244 g, 2 mmol) was added to a solution of methyltriphenylphosphonium bromide (0.7144 g, 2 mmol) in anhydrous THF (10 mL) in dry three-necked round-bottomed flask under a nitrogen atmosphere at room temperature. The mixture was stirred for 30 min. At −20°C, compound
Cobalt dichloride (0.2855 g, 1.2 mmol) was dried at 135°C under vacuum for 8 h. After cooling to room temperature, triphenylphosphine (0.9442 g, 3.6 mmol) was added to a solution of the anhydrous cobalt dichloride in anhydrous THF (10 mL) in dry three-necked round-bottomed flask under a nitrogen atmosphere at room temperature. After stirring for 30 min, sodium borohydride (0.0454 g, 1.2 mmol) was added to the mixture and then stirred for 30 min. Compound
The sex pheromones, which were synthesized and purified as presented in Scheme
Live
Two-day-old Asian Corn Borer males were slightly anaesthetized with ice for 2 min, followed by 1 min at room temperature to allow males to recover, and then they were immobilized with an insect pin. Antennae were excised from head with forceps and their last segments were cut with forceps. The antennae were then fixed to the electrodes with conducting gel Spectra 360 (Parker Lab. Inc., Hellendoorn, Netherlands). A flow of humidified pure air (1200 mL/min) was continuously directed over the male antenna through the main branch of a glass tube (7 cm long × 5 mm diameter). Test stimulations were performed by giving puffs of air (500 mL/min) for 0.5 s at 30 s intervals through a Pasteur pipette inserted onto a lateral branch of the tube, using a CS-55 stimulus controller (Syntech). The pipette contained a piece of filter paper (5 × 0.5 cm) on which the stimulus compound had been deposited. The solvent was evaporated before the tests. Control puffs over a piece of filter paper containing only hexane were intercalated between two consecutive stimuli. The signals were amplified (100x) and filtered (DC to 1 kHz) with an IDAC-2 interface (Syntech), digitized on a PC, and analyzed with the EAG Pro program. Each treatment was replicated on 6 antennae; the experiment was repeated three times [
EAG recordings were obtained from six antennal preparations for each treatment. For analyses, EAG response to the solvent control was deducted from the EAG amplitudes elicited by the test compounds. The corrected EAG data were analyzed by analysis of variance (ANOVA) followed by Tukey’s HSD test (
In summary, we have developed a new and practical route for the total synthesis of the sex pheromones of
The authors declare that they have no conflicts of interest.
Zhengchang Lu and Wei Liu contributed equally to this work.
Financial support of this research provided by Science and Technology Planning Project of Jilin Province (20140204022NY, 20160414015GH, 20160414028GH, and 20180201012NY) and National Science & Technology Pillar Program during the Thirteenth Five-Year Plan Period (2016YFD0300704 and 2017YFD0201802) is greatly acknowledged. The authors thank Fan Zhang and Su Wang from Beijing Academy of Agricultural and Forestry Sciences, Beijing, for providing EAG setup and
Copies of NMR spectra for compounds tridecane-1,13-diol (3), 13-hydroxytridecyl acetate (4), 13-oxotridecyl acetate (5), tetradec-13-en-1-yl acetate (6), and (Z/E)-12-tetradecene-1-ol acetate (1a, 1b). Copies of MS spectra for compounds 1a and 1b, (Z/E)-12-tetradecene-1-ol acetate (1a, 1b). Analysis of the ratio of (Z/E)-12-tetradecene-1-ol acetate (1a, 1b). Figure A: GC-MS analysis of the gonad extract of Asian Corn Borer [