Synthese von 2‐Desoxy‐α‐O‐glycopeptiden mit dem N‐Iodsuccinimid‐(NIS‐) Verfahren

Synthesis of 2‐Deoxy‐α‐O‐glycopeptides by the N‐Iodosuccinimide (NIS) Procedure Glycosidation of amino acid/peptide derivatives of serine, threonine, or hydroxyproline with glycals like tris‐O‐acetyl‐D‐glucal 1 or tris‐O‐acetyl‐D‐galactal 2 and N‐iodosuccinimide (NIS) gives 2‐deoxy‐2‐iodo‐α‐O‐glycopeptides with high yields and excellent anomeric purity. Disaccharide glycals like per‐O‐acetyl‐D‐cellobial 15, per‐O‐acetyl‐D‐lactal 16, and 2′,3′,4′,6′‐tetra‐O‐acetyl‐β‐D‐galactopyranosyl‐(1 – 3)‐4,6‐di‐O‐benzyl‐D‐galactal 17 can also be used as glycosyl donors in this process. They give moderate to good yields of α‐O‐glycoside with formation of small amounts of β‐O‐glycopeptide. The NIS procedure is especially favored for the direct and stereoselective glycosidation of larger peptide fragments, which is very difficult with classical techniques. The so‐formed 2‐deoxy‐2‐iodo‐α‐O‐glycopeptides were deiodinated by using different methods and then deacetylated in the sugar moiety.