A new catalyst for reductive cleavage of methylated glycans |
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| Authors: | J G Jun G R Gray |
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| Affiliation: | 1. Department of Pharmaceutical Chemistry, University of Debrecen, Debrecen, Hungary;2. Research Group for Oligosaccharide Chemistry of HAS, University of Debrecen, Debrecen, Hungary;3. Glycoptim Ltd., Debrecen, Hungary;1. Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, China;2. Key Laboratory of Diagnostics of Traditional Chinese Medicine, Collaborative Innovation Center of Digital Traditional Chinese Medicine, Hunan University of Chinese Medicine, Changsha 410208, China;3. Department of Anatomy & Neurobiology and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD 21201, USA;4. Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Program in Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA;5. National Institute of Mental Health, Bethesda, MD 20892, USA;6. Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA;7. MD Anderson Cancer Center, University of Texas, Houston, TX 77030, USA;8. Franciscan Hospital for Children, Brighton, MA 02135, USA;9. Research Center for Pharmacology and Toxicity, Chinese Academy of Medical Science & Peking Union Medical College, Institute of Medicinal Plant Development, Beijing 100193, China |
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| Abstract: | ![]()
Several per-O-methylated D-glucans and D-fructans were used as models in an attempt to identify new catalysts for carrying out reductive cleavage. Included in these model studies were several D-glucans that contained 4-linked D-glucopyranosyl residues as well as one having a 4-linked D-glucitol residue, as both types of residue had previously been found to give rise to substantial proportions of artifactual products. These studies led to the development of a new catalyst for carrying out reductive cleavage, namely, a mixture of 5 equivalents of trimethylsilyl methanesulfonate (Me3SiOSO2Me) and 1 equivalent of boron trifluoride etherate (BF3 . Et2O) per equivalent of acetal. This new catalyst was found to accomplish the reductive cleavage of per-O-methylated, 4-linked D-glucopyranosyl residues and 4-linked D-glucitol residues, to give only the expected derivatives of 1,5-anhydro-D-glucitol and D-glucitol, respectively. The mixture of Me3SiOSO2Me and BF3 . Et2O also catalyzed reductive cleavage of the D-fructofuranosyl residues of per-O-methylated sucrose and inulin, to give only the expected derivatives of 2,5-anhydro-D-mannitol and 2,5-anhydro-D-glucitol. Indeed, when used alone, Me3SiOSO2Me also rapidly catalyzed the reductive cleavage of D-fructofuranosyl residues, but, under the same conditions, D-glucopyranosyl residues were unaffected. The results of these and other model studies demonstrated that catalysis of reductive cleavage by the mixture of Me3SiOSO2Me and BF3 . Et2O occurs in a synergistic manner. Examination of the mixture of Me3SiOSO2Me and BF3 . Et2O by 1H-n.m.r. spectroscopy demonstrated that a reaction occurs to generate trimethylsily fluoride and species of the type F2BOSO2Me, FB(OSO2Me)2, or B(OSO2Me)3 via ligand exchange. |
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