Synthese von L‐Alanyl‐3‐O‐(β‐D‐xylopyranosyl)‐L‐seryl‐glycyl‐L‐isoleucin. Direkte Glycosidierung von Peptiden

Abstract

Mit 1,2,3,4‐Tetra‐O‐acetyl‐β‐D‐xylopyranose (1) in Gegenwart von Trimethylsilyltriflat und mit Ethyl‐2,3,4‐tri‐O‐benzoyl‐1‐thio‐β‐D‐xylopyranosid (4) unter Katalyse von DMTST läßt sich das Tetrapeptid 8 glycosidieren zu 10 und 9. Die Entblockierung von 10 liefert das Glycopeptid L‐Ala‐3‐O‐(β‐D‐Xylp)‐L‐Ser‐Gly‐L‐Ile (11), das die N‐terminale Aminosäuresequenz 3 bis 6 eines Proteo‐dermatansulfates darstellt.

Synthesis of S-Linked Glycoconjugates and S-Disaccharides by Thiol–Ene Coupling Reaction of Enoses

“…Hydrothiolation of the pentose-derived 2-acetoxy-glycal 3a , applying the above conditions, gave a stereoisomeric mixture of the 1,2- cis and 1,2- trans α-thioglycosides 4a and 5a in a ratio of 2:1. Analogously, reaction between ethanethiol and 3b led to the formation of both the 1,2- cis and 1,2- trans α-thioglycosides 4b and 5b .…”

Chemistry of xylopyranosides

“…BF3⋅OEt2 as catalyst (Scheme 8). 208 The method works well with other Lewis acids, such as ZrCl4, [209][210] SnCl4, 211 FeCl3, 212 MoO2Cl2, 213 or FeI3 214 . Thioxylosides can also be synthesized from an acetyl donor and TMSSMe with BF3⋅OEt2 215 or TMSOTf 216 as catalysts in moderate yields, or TMSSPh in combination with SnCl4 217 .…”

Towards the complete synthetic O-antigen of Vibrio cholerae O1, serotype inaba: improved synthesis of the conjugation-ready upstream terminal hexasaccharide determinant

“…Unlike previously, the a-acetate 11a was now obtained crystalline for the rst time. We planned to use the latter as a glycosyl donor under BF 3 $Et 2 O or TMSOTf catalysis 8,9 to make the corresponding 2-trimethylsilylethyl (SE) glycoside 13a, and perhaps also higher oligosaccharides in this series, thereby improving the economy of the overall synthesis. Unfortunately, this approach was unsuccessful: only the corresponding 1-OH compound was formed.…”