Synthesis, conformational analysis and SAR research of OSW-1 analogues

A series of novel OSW-1 analogues were synthesized by coupling disaccharides (2-O-4-methoxylbenzoyl-β-d-xylopyranosyl-(1→3)-2-O-acetyl-α-l-arabinopyranosyl) or (2-O-4-(E)-cinnamoyl-β-d-xylopyranosyl-(1→3)-2-O-acetyl-α-l-arabinopyranosyl) and their 1→4 linked analogues [(2-O-4-methoxylbenzoyl-β-d-xylopyranosyl-(1→4)-2-O-acetyl-α-l-arabinopyranosyl) or (2-O-4-(E)-cinnamoyl-β-d-xylopyranosyl-(1→4)-2-O-acetyl-α-l-arabinopyranosyl)] with three different steroidal sapogenins at 16β-hydroxy. Their conformation was analyzed with NMR spectroscopy and molecule simulation. The arabinose moiety of 1–3 linked analogues was in chair conformation and 1–4 linked analogues was in boat conformation. 1–3 linked analogues exhibited potent anti-proliferation activity against a panel of human tumor cells at nanomolar concentration level, while 1–4 linked analogues did not show antitumor activity. This work should provide an evidence that the conformation plays an important role in the antitumor activity. [Display omitted] The highest antiproliferative activity was displayed by compounds containing 1–3 linked disaccharide which had convergent structures at nanomolar concentrations level. 1–4 linked analogues which had divergent structures showed a lower activity. The key role of triangular molecular shape of 1–3 linked OSW-1 analogues for the high activity was confirmed.