A compound of Formula (I) wherein Z is -O - ; X is selected from the 5' end of a nucleoside, nucleoside analogue, oligonucleotide, or oligonucleotide analogue and Y is selected from the 3' end of a nucleoside, nucleoside analogue, oligonucleotide, or oligonucleotide analogue; -H, -OH, -SH, -O-PG, -S-PG, a linker, a monophosphate or diphosphate, or a label or quencher; or Y is selected from the 3' end of a nucleoside, nucleoside analogue, oligonucleotide, or oligonucleotide analogue and X is selected from the 5' end of a nucleoside, nucleoside analogue, oligonucleotide, or oligonucleotide analogue, -H, -OH, -SH, -O-PG, or -S-PG, a linker, a monophosphate or diphosphate, or a label or quencher; R 1 is selected from -NR 1A R 1B , -OR 3 , -SR 3 , -H, -S(O)H, -S(O)R 3 , -S(O) 2 H, -S(O) 2 R 3 , -S(O) 2 NH 2 , -S(O) 2 NHR 3 , -S(O) 2 NR 3 2 , -C 1 - 10 alkyl, -C 2 - 10 alkenyl, -C 2 - 10 alkynyl, -C 6 - 10 aryl, or -C 5-10 heteroaryl; R 2 is selected from -H, -NR 2A R 2B , -OR 3 , -SR 3 , halogen, -CN, -S(O)H, -S(O)R 3 , -S(O) 2 H, -S(O) 2 R 3 , -S(O) 2 NH 2 , -S(O) 2 NHR 3 , -S(O) 2 NR 3 2 , -C 1 - 10 alkyl, -C 2 - 10 alkenyl, -C 2 - 10 alkynyl, -C 6 - 10 aryl, or -C 5-10 heteroaryl; wherein each R 1A , R 1B , R 2A , and R 2B is independently selected from -H, -C 1 - 10 alkyl, -C 2 - 10 alkenyl, -C 2 - 10 alkynyl, -C 6 - 10 aryl, or -C 5-10 heteroaryl; optionally wherein R 1A and R 2A together form an alkylene or heteroalkylene chain of 2-4 atoms in length; optionally wherein R 1A and R 1B , together with the atom to which they are bound, form a 5-8 membered heterocycle; optionally wherein R 2A and R 2B , together with the atom to which they are bound, form a 5-8 membered heterocycle; R 3 is selected from -C 1 - 10 alkyl, -C 2 - 10 alkenyl, -C 2 - 10 alkynyl, -C 6 - 10 aryl, or -C 5-10 heteroaryl; wherein each alkyl, aryl, heteroaryl, alkylene or heteroalkylene is optionally substituted; wherein PG is a protecting group. Z is -O - ; X is selected from the 5' end of a nucleoside, nucleoside analogue, oligonucleotide, or oligonucleotide analogue and Y is selected from the 3' end of a nucleoside, nucleoside analogue, oligonucleotide, or oligonucleotide analogue; -H, -OH, -SH, -O-PG, -S-PG, a linker, a monophosphate or diphosphate, or a label or quencher; or Y is selected from the 3' end of a nucleoside, nucleoside analogue, oligonucleotide, or oligonucleotide analogue and X is selected from the 5' end of a nucleoside, nucleoside analogue, oligonucleotide, or oligonucleotide analogue, -H, -OH, -SH, -O-PG, or -S-PG, a linker, a monophosphate or diphosphate, or a label or quencher; R 1 is selected from -NR 1A R 1B , -OR 3 , -SR 3 , -H, -S(O)H, -S(O)R 3 , -S(O) 2 H, -S(O) 2 R 3 , -S(O) 2 NH 2 , -S(O) 2 NHR 3 , -S(O) 2 NR 3 2 , -C 1 - 10 alkyl, -C 2 - 10 alkenyl, -C 2 - 10 alkynyl, -C 6 - 10 aryl, or -C 5-10 heteroaryl; R 2 is selected from -H, -NR 2A R 2B , -OR 3 , -SR 3 , halogen, -CN, -S(O)H, -S(O)R 3 , -S(O) 2 H, -S(O) 2 R 3 , -S(O) 2 NH 2 , -S(O) 2 NHR 3 , -S(O) 2 NR 3 2 , -C 1 - 10 alkyl, -C 2 - 10 alkenyl, -C 2 - 10 alkynyl, -C 6 - 10 aryl, or -C 5-10 heteroaryl; wherein each R 1A , R 1B , R 2A , and R 2B is independently selected from -H, -C 1 - 10 alkyl, -C 2 - 10 alkenyl, -C 2 - 10 alkynyl, -C 6 - 10 aryl, or -C 5-10 heteroaryl; optionally wherein R 1A and R 2A together form an alkylene or heteroalkylene chain of 2-4 atoms in length; optionally wherein R 1A and R 1B , together with the atom to which they are bound, form a 5-8 membered heterocycle; optionally wherein R 2A and R 2B , together with the atom to which they are bound, form a 5-8 membered heterocycle; R 3 is selected from -C 1 - 10 alkyl, -C 2 - 10 alkenyl, -C 2 - 10 alkynyl, -C 6 - 10 aryl, or -C 5-10 heteroaryl; wherein each alkyl, aryl, heteroaryl, alkylene or heteroalkylene is optionally substituted; wherein PG is a protecting group. <EOS>