In order to develop potential glucosamine-6-phosphate synthase inhibitors and anti-fungal agents, twenty five oleanolic acid oxime esters were synthesized in an efficient way. The structures of the new compounds were confirmed by MS, HRMS, ¹H-NMR and ¹³C-NMR. Preliminary studies based on means of the Elson-Morgan method indicated that many compounds exhibited some inhibitory activity of glucosamine-6-phosphate synthase (GlmS), and the original fungicidal activities results showed that some of the compounds exhibited good fungicidal activities towards Sclerotinia sclerotiorum (Lib.) de Bary, Rhizoctonia solani Kuhn and Botrytis cinerea Pers at the concentration of 50 µg/mL. These compounds would thus merit further study and development as antifungal agents.

Botrytis cinerea is considered an important plant pathogen and is responsible for significant crop yield losses. With the frequent application of commercial fungicides, B. cinerea has developed resistance to many frequently used fungicides. Therefore, it is necessary to develop new kinds of fungicides with high activity and new modes of action to solve the increasingly serious problem of resistance. During our screening of fungicide candidates, one novel sulfonamide compound, N-(2-trifluoromethyl-4-chlorphenyl)-2-oxocyclohexyl sulfonamide (L13), has been found to exhibit good fungicidal activity against B. cinerea. In this work, the mode of action of L13 against B. cinerea and the field control effect on tomato gray mold was studied. L13 had good control against B. cinerea resistant to carbendazim, diethofencarb, and iprodione commercial fungicides in the pot culture experiments. SEM and TEM observations revealed that L13 could cause obvious morphological and cytological changes to B. cinerea, including excessive branching, irregular ramification or abnormal configuration, and the decomposition of cell wall and vacuole. L13 induced more significant electrolyte leakage from hyphae than procymidone as a positive control. L13 had only a minor effect on the oxygen consumption of intact mycelia, with 2.15% inhibition at 50 μg/mL. In two locations over 2 years, the field control effect of L13 against tomato gray mold reached 83% at a rate of 450 g ai ha⁻¹, better than the commercial fungicide of iprodione. Moreover, toxicological tests demonstrated the low toxicological effect of L13. This research seeks to provide technical support and theoretical guidance for L13 to become a real commercial fungicide.

A series of novel compounds, namely 1-(diethoxyphosphoryl)-3-(4-ones-1H-1,2,3-triazol-1-yl)propan-2-yl carboxylic esters, were designed on the basis of the diazafulvene intermediate of imidazole glycerol phosphate dehydratase (IGPD) and high-activity inhibitors of IGPD, and synthesized as inhibitors targeting IGPD in plants. Their structures were confirmed by ¹H-NMR, ¹³C-NMR, ³¹P-NMR and HR-MS. The herbicidal evaluation performed by a Petri dish culture method showed that most compounds possessed moderate to good herbicidal activities. Six compounds were chosen for further herbicidal evaluation on barnyard grass by pot experiments. 1-(Diethoxyphosphoryl)-3-(4-phenyl-1H-1,2,3-triazol-1-yl)propan-2-yl 2-(naphthalen-1-yl)acetate (5-A3) and ethyl 1-(2-acetoxy-3-(diethoxyphosphoryl)propyl)-1H-1,2,3-triazole-4-carboxylate (5-B4) showed good herbicidal activities. Compared with the compounds with the best herbicidal activity ever reported, both compounds 5-A3 and 5-B4, which can inhibit the growth of barnyard grass at the concentration of 250g/hm², efficiently gave rise to a nearly 4-fold increase of the herbicidal potency. However, their herbicidal activities were lower than that of acetochlor (62.5 g/hm²) in the pot experiments.

In order to develop potential anti-fungal agents, seven glycoconjugates composed of a-L-rhamnose, 6-deoxy-a-L-talose, b-D-galactose, a-D-mannose, b-D-xylose-(1®4)-6-deoxy-a-L-talose, b-D-galactose-(1®4)-a-L-rhamnose, b-D-galactose-(1®3)-b-D-xylose-(1®4)-6-deoxy-a-L-talose as the glycone and oleanolic acid as the aglycone were synthesized in an efficient and practical way using glycosyl trichloroacetimidates as donors. The structures of the new compounds were confirmed by MS, ¹H-NMR and ¹³C- NMR. Preliminary studies based on means of mycelium growth rate, indicated that all the compounds possess certain fungicidal activity against Sclerotinia sclerotiorum (Lib.) de Bary, Rhizoctonia solani Kuhn, Botrytis cinerea Pers and Phytophthora parasitica Dast.