Microwave-Assisted Esterification of N-Acetyl-L-Phenylalanine Using Modified Mukaiyama’s Reagents: A New Approach Involving Ionic Liquids
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Authors
Zhao, Hua
Song, Zhiyan
Cowins, Janet V.
Olubajo, Olarongbe
Issue Date
2008-01-16
Type
Article
Language
en_US
Keywords
Savannah State University (Savannah, Ga.) , Amino acid , Ionic liquid , Mukaiyama’s reagent , Microwave , Esterification
Alternative Title
Abstract
Inspired by the concept of ionic liquids (ILs), this study modified the original Mukaiyama’s reagent, 2-chloro-1-methylpyridinium iodide (m.p. 200-dec), from ionic solid into liquids by changing its anion. The esterification of N-acetyl-L-phenylalanine was investigated as a model reaction. The microwave irradiation was more effective in esterifying N-acetyl-L-phenylalanine than the conventional reflux method. The original Mukaiyama’s reagent was modified into ILs through manipulating its anion. However, only non-nucleophilic anions (such as EtSO4- and Tf2N-) were favorable since nucleophilic ones (such as CF3COO- and CH3COO-) could exchange with chlorine resulting in non-reactive coupling reagents. Two modified Mukaiyama’s compounds (i.e. hydrophilic [2- ClMePy][EtSO4] and hydrophobic [2-ClMePy][Tf2N]) have been identified as the best ILtype coupling reagents. The esterification reaction was greatly enhanced by using 1- methylimidazole as the base instead of conventional toxic tertiary amines, and by using excess amount of alcohols as solvents instead of dichloromethane. Overall, the method reported is effective and ‘greener’.
Description
Citation
Zhao, H., Song, Z., Cowins, J. V., & Olubajo, O. (2008). Microwave-Assisted Esterification of N-Acetyl-L-Phenylalanine Using Modified Mukaiyama’s Reagents: A New Approach Involving Ionic Liquids. International Journal of Molecular Sciences, 9(1), 33–44. MDPI AG. Retrieved from http://dx.doi.org/10.3390/ijms9010033
Publisher
MDPI
License
Journal
International Journal of Molecular Sciences
Volume
Issue
PubMed ID
ISSN
1422-0067