Stereocontrolling Effect of a Single Triisopropylsilyl Group in 1,2‐cis‐Glucosylation

• Published in: European journal of organic chemistry 2022-10, Vol.2022 (39), p.n/a
• Main Authors: Abronina, Polina I., Malysheva, Nelly N., Zinin, Alexander I., Kolotyrkina, Natalya G., Kononov, Leonid O.
• Format: Article
• Language: English
• Subjects: 1,2-cis-Glycosylation; Carbohydrates; Glycosylation; Nucleophiles; Stereoselectivity; Triisopropylsilyl groups
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.202200517

Glycosylation with phenyl 3,4,6‐tri‐O‐benzoyl‐2‐O‐triisopropylsilyl (TIPS)‐1‐thio‐β‐d‐glucopyranoside is highly 1,2‐cis‐stereoselective, while the use of 2,3‐di‐O‐TIPS glucosyl donor with benzoyl groups at O‐4 and O‐6 results in the loss of α‐stereoselectivity (α/β=3 : 1). Complete α‐stereocontrol with 2‐O‐TIPS substituted glucosyl donors could only be achieved in glucosylation of weak nucleophiles. In this case, the glucosylation seems to proceed along the SN1‐like pathway via the 4H3 conformer of glycosyl cation stabilized by the bulky TIPS group at O‐2. Glycosylation with thioglucosides with a single triisopropylsilyl (TIPS) group at O‐2 is highly 1,2‐cis‐stereoselective when weak nucleophiles (ROH) are used. Glycosylation proceeds along the SN1‐like pathway via glycosyl cation, which is locked in 4H3 conformation with bulky TIPS group in the pseudo‐equatorial position.