Large-Scale Preparation of the Phytoalexin Elicitor Glucohexatose and Its Application as a Green Pesticide

Abstract

Large-scale preparation of the phytoalexin elicitor was achieved through a highly regio-and sterereoselective synthesis using 2,3,4,6-tetra-O-benzoyl-D-glucopyranosyl trichloroacetimidate (1), 1,2:5,6-di-O-isopropylidene-R-D-glucofuranose (2), and 6-O-acetyl-2,3,4-tri-O-benzoyl-R-D-glucopyranosyl trichloroacetimidate (3) as the synthons. Coupling of 1 with 2 gave the 1f3-linked disaccharide; subsequent selective removal of 5,6-O-isopropylidene to give 5 followed by selective 6-O-glycosylation with 1 afforded the trisaccharide 6. Hydrolysis to remove the 1,2-O-isopropylidene was accompanied by ring expansion, giving 3,6-branched pyranosyl trisaccharide. Acetylation, selective 1-O-deacetylation, and activation with trichloroacetonitrile gave the trisaccharide donor 7. The trisaccharide acceptor 9 was prepared from condensation of the disaccharide 5 with 3 and subsequent 6-O-deacetylation. Coupling of the trisaccharide donor 7 with the trisaccharide acceptor 9 and subsequent deprotection afforded the glucohexatose elicitor. The cost of the produced glucohexatose should be low enough to allow its applications in agriculture as a green pesticide. At a concentration of 5-10 mg/L, the resultant elicitor was used to treat growing orange trees and harvested oranges, giving very encouraging results, comparable with those obtained using commercial pesticides at a concentration of 1400 mg/L (Topsin-M) for growing trees and 900 mg/L (Tecto) for harvested oranges, respectively. Treatment of tomato leaves against Botrytis cinerea with the synthetic elicitor at a concentration of 10 mg/L gave 82% inhibition, comparable with the inhibition of 84% by Wanmeiling at a concentration of 1000 mg/L. Treatment of tea leaves also showed promising results.

Antimicrobial and Cytotoxic Activities of Neolignans from Magnolia officinalis

“…The finding that the transfer of vancomycin-resistant genes to S. aureus is possible in vitro [10] and the isolation of an MRSA strain resistant to vancomycin (VRSA) [11] triggered the prompt search for new antibiotics against both VRE and MRSA. Natural products from plants hold great promise as antimicrobials [12] [13], e.g., phytoalexins [14] [15], that possess different chemical structures to present antibiotics.…”

Elicitation of Phytoalexins against Late Blight Disease in Tomato Plants by Abiotic Agents and its Impact on Disease Resistance

“…phytoalexins induction, PR proteins, enhancement of peroxidase activity, deposition of lignin … etc. ), (Kuc, 1972;Keen and Little field 1979;Kuc, 1982a;Kuc, 1982b;Jeandet et al, 1995 andNing et al, 2003).…”

A New Class of Glucosyl Thioureas: Synthesis and Larvicidal Activities

“…Numerous traditional pesticides are banned in many countries because of their high toxicity [1,2,3,4,5] and poor biodegradation [6,7,8,9,10,11]. Fortunately, green pesticides [12,13,14,15] for mimic natural pesticides [16,17,18,19,20] are efficient strategies in pesticide research and development, and pesticides from natural resources are very attractive to academic and industrial researchers due to their unique pesticidal activities, good biodegradation and environmental friendliness. Chitin is the most abundant natural polyaminosaccharide and serves as a structural component to form the skin of many arthropod pests.…”