Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India.
Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India.
Adv Carbohydr Chem Biochem. 2020;78:1-134. doi: 10.1016/bs.accb.2020.10.001.
Increasing demands for molecules with skeletal complexity, including those of stereochemical diversity, require new synthetic strategies. Carbohydrates have been used extensively as chiral building blocks for the synthesis of various complex molecules. On the other hand, the vinyl sulfone group has been identified as a unique functional group, which acts either as a Michael acceptor or a 2π partner in cycloaddition reactions. A combination of the high reactivity of the vinyl sulfone group and the in-built chiralities of carbohydrates has the potential to function as a powerful tool to generate a wide variety of enantiomerically pure reactive intermediates. Since CS bond formation in carbohydrates is easily achieved with regioselectivity, further synthetic manipulations of these thiosugars has led to the generation of a wide range of vinyl sulfone-modified furanosyl, pyranosyl, acyclic, and bicyclic carbohydrates. Several approaches have been studied to standardize the preparative methods for accessing vinyl sulfone-modified carbohydrates at least on a gram scale. Reactions of these modified carbohydrates with appropriate reagents afford a large number of new chemical entities primarily via (i) Michael addition reactions, (ii) desulfostannylation, (iii) Michael-initiated ring-closure reactions, and (iv) cycloaddition reactions. A wide range of desulfonylating reagents in the context of sensitive molecules such as carbohydrates have also been extensively studied. Applications of these strategies have led to the synthesis of (a) amino sugars and branched-chain sugars, (b) C-glycosides, (c) enantiomerically pure cyclopropanes, five- and six-membered carbocycles, (d) saturated oxa-, aza-, and thio-monocyclic heterocycles, (e) bi-and tricyclic saturated oxa and aza heterocycles, (f) enantiomerically pure and trisubstituted pyrroles, (g) 1,5-disubstituted 1,2,3-triazolylated carbohydrates and the corresponding triazole-linked di- and trisaccharides, (h) divinyl sulfone-modified carbohydrates and densely functionalized S,S-dioxothiomorpholines, and (i) modified nucleosides. Details of reaction conditions were incorporated as much as possible and mechanistic discussions were included wherever necessary.
对具有骨架复杂性的分子（包括具有立体化学多样性的分子）的需求不断增加，这需要新的合成策略。碳水化合物已被广泛用作合成各种复杂分子的手性构建块。另一方面，乙烯砜基已被确定为一种独特的官能团，它在加成反应中既可以作为迈克尔受体，也可以作为 2π 供体。乙烯砜基的高反应性和碳水化合物固有的手性的结合有可能成为产生各种对映体纯反应性中间体的有力工具。由于碳水化合物中的 CS 键形成具有区域选择性，因此对这些硫代糖的进一步合成操作导致了广泛的乙烯砜修饰呋喃糖、吡喃糖、无环和双环碳水化合物的生成。已经研究了几种方法来至少在克级规模上标准化制备乙烯砜修饰碳水化合物的方法。这些修饰的碳水化合物与适当的试剂反应，主要通过（i）迈克尔加成反应、（ii）去甲锡烷基化、（iii）迈克尔引发的环闭合反应和（iv）环加成反应，得到大量新的化学实体。在碳水化合物等敏感分子的背景下，还广泛研究了各种脱磺酰基试剂。这些策略的应用导致了（a）氨基糖和支链糖、（b）C-糖苷、（c）对映体纯环丙烷、五元和六元碳环、（d）饱和氧杂、氮杂和硫杂单环杂环、（e）双环和三环饱和氧杂和氮杂杂环、（f）对映体纯和三取代吡咯、（g）1,5-二取代 1,2,3-三唑基化碳水化合物和相应的三唑连接的二糖和三糖、（h）二乙烯砜修饰的碳水化合物和密集功能化的 S，S-二氧代硫代吗啉、和（i）修饰的核苷。尽可能纳入了反应条件的详细信息，并在必要时包括了机理讨论。
