Cross-coupling of propargylated arabinogalactan with 2-bromothiophene.

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.

Modification of arabinogalactan propargyl ethers by triazolyl functions.

Polysaccharide arabinogalactan (AG) has been modified by triazolyl functions via the copper-catalyzed 1,3-dipolar addition of azides to propargyl ethers. A range of new AG triazolo derivatives bearing benzyl, 4-vinylbenzyl, 1-naphthylmethyl, (1-vinylimidazol-2-yl)methyl, (1-ethylimidazol-2-yl)methyl, (1-vinylbenzimidazol-2-yl)methyl, allyl, carboxymethyl (as Na-salt) substituents is prepared by "one-pot" approach from organic azides generated in situ and AG propargyl ethers. The latter (degree of substitution 2.

Propargylation of arabinogalactan with propargyl halides--a facile route to new functionalized biopolymers.

New arabinogalactan propargyl ethers with degree of substitution (DS) up to 2.8 have been obtained by propargylation of arabino-3,6-galactan (AG) with propargyl bromide (PB) in the two-phase system 30-60% КОН aqueous solution/toluene in the presence of triethylbenzylammonium chloride (TEBAС) or without catalyst (ambient temperature, 1-24 h) in 20-87% yields. The highest yields have been reached using TEBAС as phase-transfer catalyst, though the non-catalytic version proves to be also efficient (DS 2.