Acta Chimica Sinica ›› 2020, Vol. 78 ›› Issue (8): 767-777.DOI: 10.6023/A20060201 Previous Articles     Next Articles



许伟长a, 刘威b, 李祥c, 徐鹏a, 俞飚a,b   

  1. a 中国科学院上海有机化学研究所 生命有机化学国家重点实验室 上海 200032;
    b 上海科技大学 物质科学与技术学院 上海 201210;
    c 香港大学 化学系 香港 999077
  • 投稿日期:2020-06-01 发布日期:2020-07-08
  • 通讯作者: 徐鹏, 俞飚;
  • 基金资助:

Synthesis of Oligosaccharides Relevant to the Substrates of Heparanase via Dehydrative Glycosylation

Xu Weichanga, Liu Weib, Li Xiangc, Xu Penga, Yu Biaoa,b   

  1. a State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China;
    b School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210;
    c Department of Chemistry, The University of Hong Kong, Hong Kong 999077
  • Received:2020-06-01 Published:2020-07-08
  • Supported by:
    Financial support from National Natural Science Foundation of China (Nos. 21621002 & 21602240), Key Research Program of Frontier Sciences of CAS (No. ZDBS-LY-SLH030), Strategic Priority Research Program of CAS (No. XDB20020000), and Youth Innovation Promotion Association of CAS (No. 2020258) are acknowledged.

Heparanase, an endo-b-D-glucuronidase responsible for specific cleavage of heparin and heparan sulfates, is relevant to a number of biological processes, such as inflammation, tumor angiogenesis and metastasis. Heparin and heparan sulfate(HS), ubiquitously distributed on the cell surface and in the extracellular matrix, play significant roles in a diverse set of biological processes, including cell growth, virus infection, and tumor metastasis. The substrate specificity of the purified recombinant human heparinase has been investigated, and an optimal tetrasaccharide substrate of heparinase was found to be DHexUA(2S)-GlcN(NS,6S)-GlcUA-GlcN(NS,6S). Here we report an efficient alternative to the chemical synthesis of oligosaccharides relevant to the substrates of heparanase, including the stereoselective construction of a-GlcN-(1→4)-GlcA glycoside bonds and the effective post-assembly manipulations on the fully elaborated oligosaccharides. The dehydrative glycosylation protocol, capitalizing on direct activation of C1-hemiacetals as glycosyl donors, was employed to construct the challenging a-GlcN-(1→4)-GlcA linkages, using diphenyl sulfoxide(Ph2SO)/triflic anhydride(Tf2O) as promoters, 2,4,6-tri-tert- butylpyrimidine(TTBP) as base, toluene as a solvent, and -60 ℃ to room temperature as the working temperature. Under these optimized conditions, mono- and disaccharide donors(9 and 10) and disaccharide acceptors(11 and 12) were condensed to provide the coupled tri- and tetrasaccharides 58 in good yields and satisfactory stereoselectivity(>65% yield and a/b>5.4/1.0). The fully elaborated oligosaccharides 58 have then been successfully transformed into the target heparin oligosaccharides 14 via an effective sequence of manipulation of the protecting groups(>52% yield for 5 steps). The post-assembly manipulations include saponification under Zemplén conditions(for removal of benzyl ester and benzoyl group), O-sulfonation with sulfur trioxide pyridine complex(for hydroxyl groups), reduction and N-sulfonation(for azido group), and high pressure hydrogenation(for removal of benzyl groups). The availability of these heparin oligosaccharides would facilitate in-depth elucidation of the substrate selectivity of heparanase and the development of an effective assay for measuring the heparanase activities.

Key words: heparanase, heparin oligosaccharide, a-(1→4) glycosidic bond, dehydrative glycosylation, chemical synthesis