一个简单而有效的S-苯基硫糖苷活化系统,即N-碘琥珀酰亚胺和催化三氟甲磺酸铜(I),可促进“单肽”,“二肽”和“三肽”的丝氨酸和苏氨酸羟基上的β-O-糖基化。相同的活化剂组合可促进含有天冬酰胺的单肽,二肽和三肽的羧酰胺β-N-糖基化,以及核苷羧酰胺和磺酰胺。三氟甲磺酸铜(I)方法的一个重要特征是,很大程度上避免了不希望的酰胺O-糖基化。对于两组重要的生物重要受体位点(H O –和–CO N H 2),β-GlcNAc等效供体被证明可以有效地提供联系。已基于整体氢解作用开发了简化的脱保护序列,该序列可顺利产生亲本糖肽。生物蛋白的核心糖肽区域Ñ -glycosylation,由N表示4 - (β- Ñ乙酰基d-2葡糖)-Asp -甘氨酸-苏氨酸-OH,已经在溶液中制备,纯化,表征为完全脱保护的(单)糖基化三肽。
Gold(I)-Catalyzed Glycosylation with Glycosyl<i>ortho</i>-Alkynylbenzoates as Donors: General Scope and Application in the Synthesis of a Cyclic Triterpene Saponin
coupling with the poorly nucleophilic amides gives satisfactory yields. Moreover, excellent α‐selective glycosylation with a 2‐deoxysugar donor and β‐selective sialylation have been realized. Application of the present glycosylation protocol in the efficient synthesis of a cyclic triterpene tetrasaccharide have further demonstrated the versatility and efficacy of this new method, in that a novel chemoselective
Using a halogen bond (XB) donor and Schreiner's thiourea as cooperative catalysts, various amides, including the asparagine residues of several peptides, were directly coupled with glycosyl trichloroacetimidates to give unique N‐acylorthoamides in good yields. Synthetic applications of N‐acylorthoamides, including rearrangement to the corresponding β‐N‐glycoside, were also demonstrated.
The direct 2-deoxyglycosylation of nucleophiles with glycals leads to biologically and pharmacologically important 2-deoxysugar compounds. Although the direct addition of hydroxyl and sulfonamide groups have been well developed, the direct 2-deoxyglycosylation of amide groups has not been reported to date. Herein, we show the first direct 2-deoxyglycosylation of amide groups using a newly designed
Novel procedures have been developed to condense benzaldehyde effectively with beta-amino acid amides to cyclic benzyl aminals. Double carbamate protection of the heterocycle resulted in fully protected chiral beta-alanine derivatives. These serve as universal precursors for the asymmetric synthesis of functionalised beta(2)-aminoacids containing acid-labile protected side chains. Diastereoselective