Co- and homocyclotrimerization reactions of protected 1-alkynyl-2-deoxyribofuranose.: Synthesis of C-nucleosides, C-di- and C-trisaccharide analogues

Cyclotrimerization of beta- or alpha-ethynyl-3,5-di-O-toluoyl-2-deoxy-D-ribofuranose with alpha,omega-diynes proceeded smoothly under Rh-catalysis to afford the corresponding beta- or a-benzene C-nucleoside derivatives. Analogous co-cyclotrimerization of alpha- or beta-propynyl- and -phenylethynyl-3,5-di-O-toluoyl-2-deoxy-D-ribofuranose with alpha,omega-diynes gave the corresponding arene derivatives only under microwave irradiation in the presence of a Rh-catalyst in moderate yields. Attempted homocyclotrimerization of beta- or alpha-ethynyl-3,5-di-O-toluoyl-2-deoxy-D-ribofuranose under Rh-catalysis led only to enynes while the use of Ru-catalyst gave the desired 1,2,4- and 1,3,5-tri-(2-deoxyribofuranose-1-yl)benzene. (c) 2008 Elsevier Ltd. All rights reserved.