Synthesis and biological testing for pesticidal activity of 8-azasteroids

Abstract

The aim of the present study is the synthesis and testing for pesticidal activities of 2,3-dimethoxy16,16-dimethyl-D-homo-8-azagona-1,3,5(10),13-tetraene-12,17a-one and 2,3-dimethoxy-16,16-dimethyl-dhomo-8-azagona-1,3,5(10),13-tetraene-12-imino-17a-one hydrochloride which could become the basis the basis of plant protection products. The first compound was obtained by condensation of 6,7-dimethoxy-2,3- dihydroisoquinoline with 2-acetyl-5,5-dimethylcyclohexane-1,3-dione. The second substance was synthesized by interaction of the first with ammonium chloride. 2-Acetyl-5,5-dimethylcyclohexane-1,3-dione was prepared by heating dimedone with acetic acid in polyphosphoric acid. 6,7-Dimethoxy-2,3-dihydroisoquinoline was synthesized in two steps. Boiling 2-(3,5-dimethoxyphenyl)ethylamine in formic acid gave the corresponding amide, which was cyclized in the presence of phosphorus oxychloride. The structure of the obtained compounds is confirmed by the data of IR, 1H NMR, UV spectra and elemental analysis. In the IR absorption spectra of 2,3-dimethoxy-16,16-dimethyl-D-homo-8-azagona-1,3,5(10),13-tetraene-12,17a-dione and 2,3-dimethoxy-16,16-dimethyl-D-homo-8-azagona-1,3,5(10),13-tetraen-12-imino-17a-one hydrochloride, enaminodiketone bands are present (1535, 1580, 1615, 1625, 1670 cm-1 ) and enimine ketone (1595, 1650, 3260 cm-1 ) groups, respectively. Their UV absorption spectra recorded in ethanol contain two absorption bands (265.303 and 268.317 nm) corresponding to ππ* transitions of the same molecular fragments. The mass spectra of the two obtained tetracycles contain peaks of molecular ions. 1H NMR spectra correspond to the structures of all obtained compounds The synthesized compounds were tested for certain types of insecticide (against Toxoptera graminum, Musca domestica, Meloidogyne incognita, Heliothis virescens, Diabrotica undecimpunctata howardi, Caenorhabditis elegans), fungicidal (against Drechslera, Erysiphe, Puccinia, Peronospora) and herbicidal (against Amaranthus retroflexus, Brassica rapa, Abutilon theophrasti, Alopecurus myosuroides, Avena fatua, Echinochloa crus galli) activities. Both synthesized compounds showed herbicidal activity against Amaranthus retroflexus, Brassica rapa, Abutilon theophrasti and insecticidal activity against Toxoptera graminum. Hydrochloride 2,3-dimethoxy-16,16-dimethyl-D-homo-8-azagon-1,3,5(10),13- tetraene-12-imino-17a-one showed insecticidal activity against Musca domestica and fungicidal activity against Drechslera.