Carbohydrates, which are ubiquitously distributed throughout the three domains of life, play significant roles in a variety of vital biological processes. Access to unique and homogeneous carbohydrate materials is important to understand their physical properties, biological functions, and disease-related features. It is difficult to isolate carbohydrates in acceptable purity and amounts from natural sources. Therefore, complex saccharides with well-defined structures are often most conviently accessed through chemical syntheses. Two major hurdles, regioselective protection and stereoselective glycosylation, are faced by carbohydrate chemists in synthesizing these highly complicated molecules. Over the past few years, there has been a radical change in tackling these problems and speeding up the synthesis of oligosaccharides. This is largely due to the development of one–pot protection, one–pot glycosylation, and one–pot protection–glycosylation protocols and streamlined approaches to orthogonally protected building blocks, including those from rare sugars, that can be used in glycan coupling. In addition, new automated strategies for oligosaccharide syntheses have been reported not only for program-controlled assembly on solid support but also by the stepwise glycosylation in solution phase. As a result, various sugar molecules with highly complex, large structures could be successfully synthesized. To summarize these recent advances, this review describes the methodologies for one-pot protection and their one-pot glycosylation into the complex glycans and the chronological developments associated with automated syntheses of oligosaccharides.

中文翻译：

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碳水化合物的“一锅”保护，糖基化和保护-糖基化策略

遍及生命的三个领域的碳水化合物在各种重要的生物学过程中均起着重要作用。获得独特且均质的碳水化合物材料对于了解其物理性质，生物学功能和疾病相关特征非常重要。从天然来源中分离出可接受纯度和数量的碳水化合物是困难的。因此，通常通过化学合成最容易地获得具有明确结构的复杂糖。碳水化合物化学家在合成这些高度复杂的分子时面临着两个主要障碍，即区域选择性保护和立体选择性糖基化。在过去的几年中，在解决这些问题和加快寡糖的合成方面发生了根本性的变化。这主要归因于一锅保护，一锅糖基化和一锅保护糖基化方案的发展，以及简化了可用于聚糖偶联的正交保护结构单元（包括稀有糖类结构单元）的方法。另外，已经报道了用于寡糖合成的新的自动化策略，不仅用于在固相支持物上的程序控制的组装，而且还通过在溶液相中的逐步糖基化来报道。结果，可以成功地合成具有高度复杂，大结构的各种糖分子。为了总结这些最新进展，本综述描述了一锅保护及其将一锅糖基化为复杂聚糖的方法，以及与寡糖自动合成相关的按时间顺序发展的方法。