Free-Radical Ring Closure to Conformationally Locked α-<scp>l</scp>-Carba-LNAs and Synthesis of Their Oligos: Nuclease Stability, Target RNA Specificity, and Elicitation of RNase H
A new class of conformationallyconstrained nucleosides, α-l-ribo-carbocyclic LNA thymidine (α-l-carba-LNA-T, LNA is an abbreviation of locked nucleic acid) analogues and a novel “double-locked” α-l-ribo-configured tetracyclic thymidine (6,7′-methylene-bridged-α-l-carba-LNA-T) in which both the sugar puckering and glycosidic torsion are simultaneously constrained, have been synthesized through a key