Three benzylated triazole-linked nonionic locked nucleoside dimers TL-t-TL, TL-t-ABzL and TL-t-CBzL have been synthesized by
Cu(I) catalyzed Huisgen-Sharpless-Meldal [3+2] cycloaddition reaction of 3'-azido-3'-deoxy-2'-O,4'-C-methylenethymidine with 3'-Obenzyl-
and 3'-O-benzyl-5'-deoxy-5'-C-ethynyl-2'-O,4'-C-methylene-4-N-benzoylcytidine, which on debenzylation afforded the corresponding
hydroxy analogs TL-t-TL and TL-t-ABzL in 69% and 63% overall yields. An effort to debenzylate TL-t-CBzL failed. Hydroxy TL-t-
TL, TL-t-ABzL have alternatively been synthesized by the reaction of azidonucleoside with 5'-deoxy-5'-C-ethynyl-2'-O,4'-Cmethylenethymidine
and 5'-deoxy-5'-C-ethynyl-2'-O,4'-C-methylene-6-N-benzoyladenosine in 79% and 76% overall yields, respectively.
Among the two Cu(I) reagents used for cycloaddition (click) reaction, CuSO4.5H2O-sodium ascorbate in THF:tBuOH:H2O (1:1:1) was
found to be better yielding than CuBr.SMe2 in THF.