Synthesis and plant growth regulation activity of α-d-ManpNAc-(1→2)-[α-l-Rhap-(1→3)-]α-l-Rhap-(1→4)-β-d-GlupNAc-(1→3)-α-l-Rhap, the repeating unit of O-antigen of Rhizobium trifolii 4s

•A pentasaccharide analog has been synthesized for the first time.•The plant growth regulation activity of this analog was studied.•The activity data shows the analog can stimulate the growth of wheat coleoptile.

The synthesis of a pentasaccharide 2 containing acetamido-2-deoxy-d-glucose and acetamido-2-deoxy-d-mannose related to the cell wall polysaccharide of Rhizobium trifolii 4s has been achieved by a [2+3] approach from commercially available l-rhamnose, d-glucose, and d-glucosamine as the starting materials. The target molecule was equipped with a p-methoxylphenyl handle at the reducing terminus to allow for further glycoconjugate formation via selective cleavage of this group. The bioassay suggested that the synthetic pentasaccharide 2 can stimulate the growth of wheat coleoptile similarly to indole-3-acetic acid (IAA), and promote the wheat seedling development before winter by seed treatment at a concentration of 20 mg/L.

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