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Remote Participation during Glycosylation Reactions of Galactose Building Blocks: Direct Evidence from Cryogenic Vibrational Spectroscopy
Author(s) -
Marianski Mateusz,
Mucha Eike,
Greis Kim,
Moon Sooyeon,
Pardo Alonso,
Kirschbaum Carla,
Thomas Daniel A.,
Meijer Gerard,
Helden Gert,
Gilmore Kerry,
Seeberger Peter H.,
Pagel Kevin
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201916245
Subject(s) - chemistry , glycosidic bond , stereoselectivity , glycosyl , anomer , ionic bonding , covalent bond , carbohydrate chemistry , spectroscopy , photochemistry , stereochemistry , ion , catalysis , organic chemistry , physics , quantum mechanics , enzyme
The stereoselective formation of 1,2‐ cis ‐glycosidic bonds is challenging. However, 1,2‐ cis ‐selectivity can be induced by remote participation of C4 or C6 ester groups. Reactions involving remote participation are believed to proceed via a key ionic intermediate, the glycosyl cation. Although mechanistic pathways were postulated many years ago, the structure of the reaction intermediates remained elusive owing to their short‐lived nature. Herein, we unravel the structure of glycosyl cations involved in remote participation reactions via cryogenic vibrational spectroscopy and first principles theory. Acetyl groups at C4 ensure α‐selective galactosylations by forming a covalent bond to the anomeric carbon in dioxolenium‐type ions. Unexpectedly, also benzyl ether protecting groups can engage in remote participation and promote the stereoselective formation of 1,2‐ cis ‐glycosidic bonds.