Cross-coupling of propargylated arabinogalactan with 2-bromothiophene

• Sonogashira coupling of propargylated AG with 2-bromothiophene.
• The degree of substitution acetylenic hydrogen for thiophene reached 1.4–1.6.
• The structure of 3-(2-Thienyl)propynyl arabinogalactans was confirmed by IR and NMR.

Novel pharmacologically prospective derivatives of arabinogalactan (a polysaccharide from larch wood) containing acetylenic and thiophene moieties have been obtained in up to 90% yield by cross-coupling of propargylic ethers of arabinogalactan with 2-bromothiophene. The reaction proceeds in the presence of the catalytic system Pd(Ph3P)4/CuBr/LiBr and piperidine in DMSO at 80–85 °С. An advantageous feature of the synthesis is that it requires 5–25 times lesser catalytic loading than in common Sonogashira protocols thus making the reaction particularly beneficial to synthesize pharmaceutically-oriented polysaccharides.