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Single‐Step Glycosylations with 13 C‐Labelled Sulfoxide Donors: A Low‐Temperature NMR Cartography of the Distinguishing Mechanistic Intermediates
Author(s) -
Santana Andrés G.,
MontalvilloJiménez Laura,
DíazCasado Laura,
Mann Enrique,
JiménezBarbero Jesús,
Gómez Ana M.,
Asensio Juan Luis
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202003850
Subject(s) - sulfonium , chemistry , glycosyl , acceptor , glycosyl donor , adduct , yield (engineering) , sulfoxide , reactive intermediate , stereochemistry , catalysis , organic chemistry , salt (chemistry) , materials science , physics , metallurgy , condensed matter physics
Abstract Glycosyl sulfoxides have gained recognition in the total synthesis of complex oligosaccharides and as model substrates for dissecting the mechanisms involved. Reactions of these donors are usually performed under pre‐activation conditions, but an experimentally more convenient single‐step protocol has also been reported, whereby activation is performed in the presence of the acceptor alcohol; yet, the nature and prevalence of the reaction intermediates formed in this more complex scenario have comparatively received minimal attention. Herein, a systematic NMR‐based study employing both 13 C‐labelled and unlabelled glycosyl sulfoxide donors for the detection and monitoring of marginally populated intermediates is reported. The results conclusively show that glycosyl triflates play a key role in these glycosylations despite the presence of the acceptor alcohol. Importantly, the formation of covalent donor/acceptor sulfonium adducts was identified as the main competing reaction, and thus a non‐productive consumption of the acceptor that could limit the reaction yield was revealed.