36382-86-2Relevant academic research and scientific papers
Chloroaniline/lignin conjugates as model system for nonextractable pesticide residues in crop plants
Lange, B. Markus,Hertkorn, Norbert,Sandermann Jr., Heinrich
, p. 2113 - 2118 (1998)
In vitro lignins formed by the peroxidase/H2O2-mediated polymerization of coniferyl alcohol in the presence of 3,4-dichloroaniline or [15N]aniline were studied by 1H, 13C, and 15N NMR spectroscopy. The anilines were >95% bound to the benzylic α-position of lignin side chains. Mild acid hydrolysis under simulated stomach conditions (0.1 M HCl, 37 °C) was studied as a first estimate of animal bioavailability. The two extremes of facile or slow acid hydrolysis that are known for chloroaniline/lignin complexes could be reproduced by using low or high incorporation ratios of aniline to coniferyl alcohol (10 or 40 mol %, respectively). The case of facile acid hydrolysis and high animal bioavailability may be due to the high mole ratios used and may not be relevant for pesticidal crop plant residue levels of 3,4- dichloroaniline. The latter are typically in the parts per million range. On the basis of 15N NMR spectral fine structure, we propose that the acid- labile linkage may be due to anchimeric assistance in conformers formed at the high aniline molar ratio. The optimized methods presented here allow the use of in vitro lignin copolymers as a reference system for the structural features and the bioavailability of nonextractable pesticide residues in crop plants. In vitro lignins formed by the peroxidase/H2O2-mediated polymerization of coniferyl alcohol in the presence of 3,4-dichloroaniline or [15N]aniline were studied by 1H,13C, and 15N NMR spectroscopy. The anilines were >95% bound to the benzylic α-position of lignin side chains. Mild acid hydrolysis under simulated stomach conditions (0.1 M HCl, 37 °C) was studied as a first estimate of animal bioavailability. The two extremes of facile or slow acid hydrolysis that are known for chloroaniline/lignin complexes could be reproduced by using low or high incorporation ratios of aniline to coniferyl alcohol (10 or 40 mol %, respectively). The case of facile acid hydrolysis and high animal bioavailability may be due to the high mole ratios used and may not be relevant for pesticidal crop plant residue levels of 3,4-dichloroaniline. The latter are typically in the parts per million range. On the basis of 15N NMR spectral fine structure, we propose that the acid-labile linkage may be due to anchimeric assistance in conformers formed at the high aniline molar ratio. The optimized methods presented here allow the use of in vitro lignin copolymers as a reference system for the structural features and the bioavailability of nonextractable pesticide residues in crop plants.
Lignin-Biosynthetic Study: Reactivity of Quinone Methides in the Diastereopreferential Formation of p-Hydroxyphenyl- and Guaiacyl-Type β- O-4 Structures
Zhu, Xuhai,Akiyama, Takuya,Yokoyama, Tomoya,Matsumoto, Yuji
, p. 2139 - 2147 (2019)
p-Quinone methides are involved in lignin biosynthesis as transient intermediates, and the aromatization step has a great impact on the chemical structure of the resulting lignin. A series of quinone methides (QMs) were synthesized and allowed to react wi
Adducts of Anthrahydroquinone and Anthranol with Lignin Model Quinone Methides. 1. Synthesis and Characterization
Landucci, Lawrence L.,Ralph, John
, p. 3486 - 3495 (2007/10/02)
Adduct formation of anthrahydroquinone (9,10-dihydroxyanthracene, AHQ) or anthranol (9-hydroxyanthracene) with lignin model quinone methides (4-methylenecyclohexa-2,5-dienones) was established.This reaction is thought to be the key step in AHQ-catalyzed delignification of wood under alkaline pulping conditions.Numerous quinone methides derived from both 1-aryl-2-O-arylethyl and 1-aryl-2-O-arylpropyl lignin models were used.A typical example is the reaction of the quinone methide derived from 1-(3-methoxy-4-hydroxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol with AHQto give the adduct threo-1-(3-methoxy-4-hydroxyphenyl)-1-(10-hydroxy-9-oxoanthracen-10-yl)-2-(2-methoxyphenoxy)propan-3-ol. 1H NMR spectra of the adducts revealed large diamagnetic shifts of the protons in the 1-aryl substituent due to its close approach to the shielding regions of the anthracenyl moiety.This effect dimished with increasing size of the 10-substituent (H to OH to OAc).In AHQ adducts, intense hydrogen bonding between the 10-OH and the ether oxygen of the 2-aryl ether substituent was indicated by a large paramagnetic shift of the hydroxyl proton.The unusually large diamagnetic and paramagnetic shifts reflect a distinct rigidity of the adduct conformation that is more pronounced in the adducts containing a propyl side chain.
