Synthesis of D-arabinofuranosylated probes towards the functional analysis of mycobacterial arabinan degrading enzymes

Session: 
S7.2 Bacterial cell-wall modification
Code: 
OL7.2.4
Location (hall): 
Mannose
Start/end time: 
Wednesday, July 3, 2019 - 12:30 to 12:45
Akihiro
Ishiwata

Akihiro Ishiwata1, Yukishige Ito1

1Riken, Wako, Japan

Degrading enzymes of arabinan from mycobacterial cell wall had been identified [1] and their function began to attract our attention from not only a biological but also a synthetic point of view. Mycobacterial arabinan as the substrate of the enzymes involves only D-form of arabinose whereas only L-arabinose is one of the components of plant cell wall and has been found as a common constituent of both arabinogalactan (AG) and lipoarabinomannan (LAM), which are attracting particular attention among furanoside-containing glycans [2]. The functions and the mechanisms of the enzymes have not been reported in detail yet due to the limited supply of pure substrate with well defined structure for the precise biological and enzymatic studies of mycobacterial arabinan degrading enzymes. Here, we wish to report the synthesis of D-arabinofuranosylated probes towards the functional analysis of mycobacterial arabinan degrading enzymes.

We have been already studying on the synthesis of mycobacterial [3–5] and plant oligo-D-arabinofuranosides. The construction of substrate probe including some typical fragment structures with long and short as well as linear and branched structures, which possess 1,2-acetonde in the reducing residue as the small tag moiety for MASS analysis, has been achieved in stereoselective manner. As we reported previously the synthesis of docosasaccharide arabinan (Araf₂₂) fragment [5], we synthesized PNP D-Araf and various mycobacterial arabinan fragments as the substrate basically using the similar synthetic methodology. Synthesis of liner Araf₃ and Araf₉ and also branched Araf₅ and Araf₈ has been completed in stereoselective manner. As one of the expected product during the cleavage of Araf₈ and Araf₅-acetonide by arabinanase [1], a branched Araf₄ derivative has been synthesized, also as methyl glycoside.

References: 
  1. Kotani, S. et al., Biken J. 1971, 14, 379.
  2. Bhamidi, S. et al. J. Biol. Chem. 2008, 283, 12992.
  3. Ishiwata, A. et al., Bioorg. Med. Chem. 2006, 14, 3049.
  4. Ishiwata, A. et al., Lett. 2006, 8, 5525. 
  5. Ishiwata, A.; Ito, Y. J. Am. Chem. Soc. 2011, 133, 2275.

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