Precise Synthesis of Highly Branched Angelica dahurica Polysaccharides up to 66 Units Reveals a Minimal Motif for Wound Repair

Polysaccharides derived from Angelica dahurica exhibit potent wound healing activity, yet the pronounced structural heterogeneity of natural extracts has obscured the identity of the active motif and hindered clinical translation. Here we report a convergent, one-pot 22+22+22 glycosylation strategy based on glycosyl donor preactivation that enables the precise chemical synthesis of a 66-unit A. dahurica polysaccharide. This approach facilitates the efficient assembly of a comprehensive glycan library spanning tetrasaccharides to the full-length 66-mer polysaccharide, allowing for systematic biological evaluation. Functional screening identifies the reducing end hexasaccharide as the minimal active motif responsible for wound healing activity. Mechanistic analyses reveal that the synthetic hexa- and dodecasaccharides promote fibroblast and keratinocyte proliferation and migration, while concurrently reprogramming macrophage polarization. Crucially, gram-scale synthesis of both glycans enables definitive in vivo evaluation, demonstrating significantly accelerated wound closure through attenuation of excessive inflammation and promotion of organized collagen deposition. Collectively, these findings establish a general paradigm for deconvoluting heterogeneous natural polysaccharide extracts through de novo synthesis of structurally well-defined glycans as precision-engineered wound healing therapeutics.