Alginate is a biocompatible and industrially relevant polysaccharide that derives many of its important properties from the charged carboxylate groups within its polyuronic acid backbone. The design and inclusion of isosteric replacements for these carboxylates would underpin provision of new oligo-/polysaccharide materials with alternate physicochemical properties. Presented herein is our synthesis of mannuronic acid building blocks, appropriately modified at the carboxylate C6 position with a bioisosteric tetrazole. Thioglycosides containing a protected C6-tetrazole are accessed from a C6-nitrile, through dipolar cycloaddition using NaN₃ with n-Bu₂SnO. We also demonstrate access to orthogonally C4-protected donors, suitable for iterative oligosaccharide synthesis. The development of these building blocks is showcased to access anomeric 3-aminopropyl- and 1-phosphate free sugars containing this non-native motif.

中文翻译：

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C6-四唑ᴅ-甘露糖结构单元的化学合成和获得甘露糖醛酸1-磷酸的生物电子等排体

海藻酸盐是一种生物相容性和工业相关的多糖，其许多重要特性源自其多糖醛酸骨架内的带电荷羧酸根基团。这些羧酸盐的等排替代物的设计和包含将支持提供具有替代物理化学性质的新寡糖/多糖材料。本文介绍了我们合成的甘露糖醛酸结构单元，在羧基 C6 位置用生物等排四唑进行了适当修饰。通过使用 NaN ₃和n -Bu _{2 的}偶极环加成，从 C6-腈获得含有受保护的 C6-四唑的硫糖苷锡。我们还展示了对正交 C4 保护供体的访问，适用于迭代寡糖合成。展示了这些构建块的开发，以获取含有这种非天然基序的异头 3-氨基丙基-和 1-磷酸游离糖。