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Influence of Functional Groups towards the β‐Selective Glycosylation of 2‐Azido‐2‐deoxy Glycosyl Thioglycosides
Author(s) -
Gucchait Arin,
Kundu Monalisa,
Manna Tapasi,
Shit Pradip,
Misra Anup Kumar
Publication year - 2020
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.202000392
Subject(s) - chemistry , glycosyl , trifluoromethanesulfonate , glycosylation , glycosyl donor , glycoside , stereochemistry , triflic acid , anomer , organic chemistry , catalysis , biochemistry
The influence of the functional groups present in the glycosyl donor on the stereoselective glycosylation of 2‐azido‐2‐deoxy sugar thioglycosides under the N ‐iodosuccinimide (NIS) and triflic acid (TfOH) mediated glycosylation conditions has been studied in detail. It was observed that beta glycosides of 2‐azido‐2‐deoxy sugar are formed mainly via a stable alpha‐glycosyl triflate intermediate followed by S N 2 substitution of the triflate group by the acceptor. The presence of an electron withdrawing functional group such as O ‐picoloyl (Pico) in the glycosyl donor facilitates the formation of stable α‐glycosyl triflate to furnish β‐glycosides, whereas the presence of an electron donating hydrogen bond mediating functional group such as p ‐methoxybenzyl (PMB) in the glycosyl donor directs the formation of 1,2‐ cis glycosides via the glycosyl oxycarbenium ion intermediate with B 2,5 and 4 H 3 conformation. Excellent yields of the β‐glycosides were obtained in case of 2‐azido‐2‐deoxy‐ d ‐mannose and 2‐azido‐2‐deoxy‐ d ‐galactose thioglycosides, and 2‐azido‐2‐deoxy‐ d ‐glucose thioglycosides furnish moderate yields of the β‐glycosides.