Stereoselective Synthesis and Immunological Evaluation of Common O‐antigen of <i>P. mirabilis</i><scp>OE</scp> and <i>P. vulgaris</i><scp>TG103</scp>
Xiaopei Wu, Jinsheng Lai, Kexin Yang, Yunxia Xue, Jin‐Xi Liao, Liming Wang, Jiansong Sun, Jing Hu, Jian Yin, Qingju Zhang
Abstract
Comprehensive Summary Proteus species especially Proteus mirabilis and Proteus vulgaris are zoonotic pathogens which can cause public health disease. Owing to their antibiotic‐resistance, developing vaccines against these pathogens is urgently required. Herein, we describe the first synthesis of the common O‐antigen of Proteus mirabilis OE and Proteus vulgaris TG 103. The repeating unit incorporates two challenging 1,2‐ cis ‐glycosidic bonds: the 1,2‐ cis ‐2‐acetamido‐2‐deoxy‐glucosidic bonds were successfully constructed by use of conformation‐restrained 2‐nitroglucal donor under bifunctional organothiourea catalysis; while the 1,2‐ cis ‐2‐acetamido‐2‐deoxy‐galactosidic bonds were formed by use of di‐ tert ‐butylsilylidene protected 2‐azidogalactose donors. The synthetic fragments were screened by glycan microarray with immunized rabbit sera against purified LPS from Proteus mirabilis O54. The results revealed that the synthetic common O‐antigens both hexasaccharide 2 and nonasaccharide 3 can strongly bind with the IgG antibodies (Abs) in the sera, which is highly valuable for further immunological investigation in synthetic carbohydrate‐based vaccine development.