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2-O-N-Benzylcarbamoyl as a Protecting Group To Promote β-Selective Glycosylation and Its Applications in the Stereoselective Synthesis of Oligosaccharides.

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Title: 2-O-N-Benzylcarbamoyl as a Protecting Group To Promote β-Selective Glycosylation and Its Applications in the Stereoselective Synthesis of Oligosaccharides.
Authors: Yin-Jen Lu1, Yen-Hsun Lai1, You-Yu Lin1, Yi-Chi Wang1, Pi-Hui Liang1 phliang@ntu.edu.tw
Source: Journal of Organic Chemistry. 4/6/2018, Vol. 83 Issue 7, p3688-3701. 14p.
Abstract: This study examines the utility of the N-benzylcarbamoyl (BnCar) protecting group in glycosylation reactions of the parent O-2 protected carbohydrate donor. It was found that the BnCar group imparted exclusively β-selectivity with primary and secondary alcohols. A mechanistic study revealed the activated intermediate to be the glycosyl triflate in a skew conformation, which results in β-selective glycosylation via an SN2-like pathway. The BnCar group can be readily cleaved using tetrabutylammonium nitrite, without affecting ester and ether protecting groups. Taken together, these results show BnCar to be useful for the synthesis of complex oligosaccharides, an undertaking that requires delicate chemical differentiation of various protecting groups. [ABSTRACT FROM AUTHOR]
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Abstract:This study examines the utility of the N-benzylcarbamoyl (BnCar) protecting group in glycosylation reactions of the parent O-2 protected carbohydrate donor. It was found that the BnCar group imparted exclusively β-selectivity with primary and secondary alcohols. A mechanistic study revealed the activated intermediate to be the glycosyl triflate in a skew conformation, which results in β-selective glycosylation via an SN2-like pathway. The BnCar group can be readily cleaved using tetrabutylammonium nitrite, without affecting ester and ether protecting groups. Taken together, these results show BnCar to be useful for the synthesis of complex oligosaccharides, an undertaking that requires delicate chemical differentiation of various protecting groups. [ABSTRACT FROM AUTHOR]
ISSN:00223263
DOI:10.1021/acs.joc.8b00047