- Profiling of the formation of lignin-derived monomers and dimers from: Eucalyptus alkali lignin
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Lignin is a renewable and the most abundant aromatic source that can be used for extensive chemicals and materials. Although approximately 50 million tons of lignin are produced annually as a by-product of the pulp and paper industry, it is currently underutilized. It is important to know the structural features of technical lignin when considering its application. In this work, we have demonstrated the formation of low-molecular-weight constituents from hardwood (Eucalyptus) lignin, which produces much more low-molecular-weight constituents than softwood (spruce) lignin, after a chemical pulping process, and analyzed the micromolecular compositions in the alkali lignin after fractionation by dichloromethane (DCM) extraction. By applying analytical methods (gel-permeation chromatography, 2D NMR and GC-MS) with the aid of evidence from authenticated compounds, a great treasure trove of lignin-derived phenolic compounds from Eucalyptus alkali lignin were disclosed. Except for some common monomeric products, as many as 15 new lignin-derived monomers and dimers including syringaglycerol, diarylmethane, 1,2-diarylethanes, 1,2-diarylethenes, (arylvinyl ether)-linked arylglycerol dimers and isomeric syringaresinols were identified in the DCM-soluble fraction. Regarding the formation and evolution of the Cα-condensed β-aryl ether structure, a novel route that is potentially responsible for the high content of β-1 diarylethenes and diarylethanes in the lignin low-molecular-weight fraction, in addition to the β-1 (spirodienone) pathway, was proposed. This work not only provides novel insights into the chemical transformation of S-G lignin during the alkali pulping process, but also discovered lignin-derived phenolic monomers and dimers that can potentially be used as raw materials in the chemical or pharmaceutical industries. This journal is
- Hu, Zhenhua,Li, Suxiang,Lu, Fachuang,Shi, Lanlan,Wang, Chen,Yue, Fengxia,Zhang, Han,Zhao, Chengke
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supporting information
p. 7366 - 7375
(2020/11/18)
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- STEREOSELECTIVE TOTAL SYHTHESIS OF (+/-)-PEPEROMIN C
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A simple and efficient stereoselective total synthesis of (+/-)-peperomin C (1) was performed employing the 1,4-addition reaction of the organolithium salt (10) to the 3-methyl-2(5H)furanone (7) catalized by cuprous iodide as the key step.On the other han
- Cruz-Almanza, Raymundo,Higareda, Fernando Padilla
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p. 2323 - 2330
(2007/10/02)
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- 2,4-Diamino-5-benzylpyrimidines and analogues as antibacterial agents. II. C-alkylation of pyrimidines with Mannich bases and application to the synthesis of trimethoprim and analogues
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A new route to 5-(p-hydroxybenzyl)pyrimidines has been developed which utilizes phenolic Mannich bases plus pyrimidines containing at least two activating groups. The products can be alkylated on the phenolic oxygen or on the pyrimidine N-1 atom, depending on conditions. This method has been used to prepare trimethoprim, a broad-spectrum antibacterial agent, starting from 2,4-diaminopyrimidine and 2,6-dimethoxyphenol.
- Roth,Strelitz,Rauckmann
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p. 379 - 384
(2007/10/02)
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- 2,4-Diamino-5-benzylpyrimidines and Analogues as Antibacterial Agents. 3. C-benzylation of Aminopyridines with Phenolic Mannich Bases. Synthesis of 1- and 3-Deaza Analogues of Trimethoprim.
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Electrophilic substitution of 2,4-diaminopyridine by 2,6-disubstituted-4-phenols and by halogens (bromine and fluorine) produces 3-benzyl and 3-halo derivatives, plus a small amount of disubstitution at the 3,5 positions.Treatment of a 2,4-diamino-3-halopyridine with phenolic Mannich bases gives 5- and N-benzylation. 2,4-Diamino-3-bromo-5-(4-hydroxy-3,5-dimethoxybenzyl)pyridine was methylated on the phenolic group in good yield and dehalogenated to produce 3-deazatrimethoprim .This compound is about 300-fold less active as an inhibitor of Escherichia coli dihydrof olate reductase than is trimethoprim. 2,6-Diaminopyridine is very readily dibenzylated at the 3,5 positions, as well as on an amino group, by a phenolic Mannich base; use of a fourfold excess of the pyridine provided a 3-benzylated 2,6-diaminopyridine in 50percent yield; this was inactive as an inhibitor of dihydrofolate reductase at 10-4 M. 2-Amino- and 4-aminopyridines do not produce C-benzylated products under the conditions reported here.
- Rauckman, Barbara S.,Roth, Barbara
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p. 384 - 391
(2007/10/02)
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