Browsing by Author "Chou, Cheng-Ting"

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Diversity-Oriented Synthesis of Angular Bis-benzimidazole Derivatives under Microwave Irradiation
(2009-11-01)
Chen, Chih-Hau
;
Chien, Ming-Hsien
;
Kuo, Min-Liang
;
Chou, Cheng-Ting
;
Lai, Jin-Ji
Pharmaceutically interesting, angular bis-benzimidazoles with three appendages have been synthesized successfully through a diversity-oriented approach with soluble support under microwave irradiation. Polymer immobilized o-phenylenediamine was selectively N-acylated with 2-chloro-3-nitrobenzoic acid in a primary aromatic amino moiety. The obtained amide was cyclized to benzimidazole in an acidic condition, and subsequently nucleophilic aromatic substitution with different amines was performed. Successive reduction, cyclization with various aldehydes and activated isothiocyanates yielded angular biheterocyclic benzimidazoles in good quantities. Reaction progress on polymer support was precisely monitored using the conventional proton NMR spectroscopy. Preliminary screening results showed some of these interesting compounds exhibited moderately to good inhibition against vascular endothelial growth factor receptor 3 (VEGFR-3), which is related to invasion and migration of cancer cells.
Microwave assisted straightforward synthetic method for benzimidazole linked quinoxalinones on soluble polymer support
(2011-03-18)
Chou, Cheng-Ting
;
Yellol, Gorakh S.
;
Chang, Wong-Jin
;
Sun, Mei-Lian
;
Sun, Chung-Ming
The simple and efficient method was developed for the synthesis of benzimidazole linked quinoxalinones on soluble polymer support using microwave conditions. The acid catalyzed condensation of 4-fluoro-3-nitrobenzoic acid with polymer immobilized o-phenylenediamine, ipso-fluoro nucleophilic substitution with various primary amines and cyclization with acetyl chloride are the key steps involved in implemented linear synthesis. In key cyclization step, the regioselective N-acylation at secondary amine with chloroacetyl chloride followed by spontaneous intramolecular ring closure through ortho-amine functionality generate the quinoxaline skeleton under microwave irradiation. The removal of polymer support and exposure of quinoxalines for auto-oxidation finally produce the benzimidazole linked quinoxalinone derivatives with high purity and yields. (C) 2011 Elsevier Ltd. All rights reserved.
Microwave-Enhanced Efficient Regioselective Synthesis of 1,3,4-Trisubstituted 2-Mercaptoimidazoles on a Soluble Support
(2012-01-01)
Yellol, Gorakh S.
;
Chou, Cheng-Ting
;
Chang, Wang-Jin
;
Maiti, Barnali
;
Sun, Chung-Ming
A novel efficient synthetic method for regioselective synthesis of optically active 2-mercaptoimidazoles with three points of structural diversity was investigated on a polyethylene glycol (PEG) support. The key synthetic steps involve (i) synthesis of thiourea derivatives of polymer-supported amino acids with isothiocyanates and (ii) one-pot regioselective condensation of PEG-linked thiourea with a-bromo ketones to furnish the 2-mercaptoimidazole skeleton under microwave conditions. An excellent regioselectivity was observed during this one-pot condensation reaction which was further supported by NOE studies. In addition to three sets of structural diversity, supplementary chirality at the a-position of the 2-mercaptoimidazole skeleton is the key feature of this synthesis. A representative set of 2-mercaptoimidazoles was efficiently assembled on soluble support utilizing various L-amino acids, isothiocyanates and a-bromoaryl ketones with good yields.
Traceless synthesis of diketopiperazine fused tetrahydro-beta-carbolines on soluble polymer support
(2011-05-01)
Chanda, Kaushik
;
Chou, Cheng-Ting
;
Lai, Jin-Ji
;
Lin, Shu-Fen
;
Yellol, Gorakh S.
The Pictet-Spengler reaction, using polyethylene glycol immobilized tryptophan ester with a variety of ketones, was achieved by refluxing condition in acidic chloroform. The linear as well as cyclic ketones were employed. All the ketones were reacted within 6-8 h to furnish soluble polymer-supported tetrahydro-beta-carboline in good yields. Further expansion at N-terminus of tetrahydro-beta-carbolines was achieved through a reaction with chloroacetyl chloride. Finally, the 2,5-diketopiperazine skeleton was constructed over a beta-carboline by amination of the resulting N-chloroacetamides and subsequent intramolecular cyclization leading to cleavage of the polymer; constitutes a traceless synthesis of tetracyclic molecular architecture. Significantly, this strategy affords a straightforward and efficient approach for the construction of biological promising molecules with high purity and good yields.