Stereodirecting effects of 4-O-ortho-cyanobenzyl ether on chemical glycosylation with glucopyranosyl donor
Here we report a systematic investigation on the stereodirecting effects of a 4-O-ortho-cyanobenzyl ether (oBCN) group with a glucopyranosyl donor. Experimental studies revealed that the glycosylation reactions using this donor generally show dual-stereoselectivities depending on the acceptor nucleo...
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| Main Authors: | , , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | English |
| Published: |
2023
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| Subjects: | |
| Online Access: | https://hdl.handle.net/10356/168881 |
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| Institution: | Nanyang Technological University |
| Language: | English |
| Summary: | Here we report a systematic investigation on the stereodirecting effects of a 4-O-ortho-cyanobenzyl ether (oBCN) group with a glucopyranosyl donor. Experimental studies revealed that the glycosylation reactions using this donor generally show dual-stereoselectivities depending on the acceptor nucleophilicity, that is, glycosylation of weak nucleophile acceptors generally affords α-glycosides specifically while glycosylation of strong nucleophile acceptors affords β-glycosides preferentially. DFT computations suggested that strong nucleophiles preferentially attack the predominant covalent α-glycosyl triflate intermediate in an SN2-like manner, while weak nucleophiles preferentially attack the less stable and more reactive β-glycosyl triflate with H-bond mediated direction. The first and facile synthesis of a hexasaccharide repeating unit of serotype IV group B Streptococcus capsular polysaccharide demonstrated the versatile utility of glucosyl building blocks with an oBCN functionality in carbohydrate chemistry. |
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