Reagents useful for synthesizing rhodamine-labeled oligonucleotides
The present disclosure provides reagents that can be used to label synthetic oligonucleotides with rhodamine dyes or dye networks that contain rhodamine dyes.
1. An oligonucleotide comprising a label moiety produced by reacting an oligonucleotide attached to a solid support with a reagent having a structure of formula (VII):
LM-L-PEP (VII)
wherein PEP is a phosphate ester precursor group, L is an optional linker linking the label moiety to the phosphate ester precursor group and LM comprises an N-protected NH-rhodamine moiety selected from the group consisting
of structures having formulae (IIIa), (IIIb) and (IIIc):
wherein:
R′ is selected from the group consisting of R 3′ and hydrogen;
R″ is selected from the group consisting of R 6′ and hydrogen;
R 9 is a protecting group having a structure of the formula —C(O)R 10 , wherein R 10 is selected from the group consisting of hydrogen, a lower alkyl, —CX 3 ,—CHX 2 , —CH 2 X, —CH 2 —OR d and phenyl optionally mono-substituted with a lower alkyl, —X, —OR d , cyano or nitro group, wherein R d is selected from the group consisting of a lower alkyl, phenyl and pyridyl, and each X is a halo group;
each of R 1′ , R 2′ , R 2″ , R 4′ , R 4″ , R 5′ , R 5″ , R 7′ , R 7″ , R 8′ , R 4 , R 5 , R 6 , and R 7 , when taken alone, is independently selected from the group consisting of hydrogen, a lower alkyl, a (C6-C14) aryl, a (C7-C20) arylalkyl, a 5-14 membered heteroaryl, a 6-20 membered heteroarylalkyl, —R b and —(CH 2 ) x —R b , wherein x is an integer having the value between 1 and 10 and R b is selected from the group consisting of —X, —OH, —OR a , —SH, —SR a , —NH 2 , —NHR a , —NR c R c , —N + R c R c R c , perhalo lower alkyl, trihalomethyl, trifluoromethyl, —B(OH) 3 ,—B(OR a ) 3 , —B(OH)O − , —B(OR a ) 2 O − , —B(OH)(O − ) 2 , —B(OR a )(O − ) 2 , —P(OH) 2 , —P(OH)O − , —P(OR a ) 2 , —P(OR a )O − , —P(O)(OH) 2 , —P(O)(OH)O − , —P(O)(O − ) 2 , —P(O)(OR a ) 2 , —P(O)(OR a )O − , —P(O)(OH)(OR a ), —OP(OH) 2 , —OP(OH)O − , —OP(OR a ) 2 , —OP(OR a )O − , —OP(O)(OH) 2 , —OP(O)(OH)O − , —OP(O)(O − ) 2 , —OP(O)(OR a ) 2 , —OP(O)(OR a )O − , —OP(O)(OR a )(OH), —S(O) 2 O − , —S(O) 2 OH, —S(O) 2 R a , —C(O)H, —C(O)R a , —C(S)X, —C(O)O − , —C(O)OH, —C(O)NH 2 , —C(O)NHR a , —C(O)NR c R c , —C(S)NH 2 , —C(O)NHR a , —C(O)NR c R c , —C(NH)NH 2 , —C(NH)NHR a , and —C(NH)NR c R c , wherein X is halo, each R a is independently selected from the group consisting of a lower alkyl, a (C6-C14) aryl, a (C7-C20) arylalkyl, a 5-14 membered heteroaryl and a 6-20 membered heteroarylalkyl, and each R c is independently an R a , or, alternatively, two R c bonded to the same nitrogen atom may be taken together with that nitrogen atom to form a 5- to 8-membered saturated or unsaturated ring that may optionally include one or more of the same or different ring heteroatoms selected from the group consisting of O, N and S;
or, alternatively, R 1′ and R 2′ or R 7′ and R 8′ are taken together with the carbon atoms to which they are bonded to form an optionally substituted (C6-C14) aryl bridge and/or R 4′ and R 4″ and/or R 5′ and R 5″ are taken together with the carbon atoms to which they are bonded to form a benzo group; and
each of R 3′ and R 6′ , when taken alone, is independently selected from the group consisting of a lower alkyl, a (C6-C14) aryl, a (C7-C20) arylalkyl, a 5-14 membered heteroaryl and a 6-20 membered heteroarylalkyl, or alternatively, R 3′ and R 2′ or R 4′ and/or R 6′ and R 5′ or R 7′ in the compounds of structural formula (IIIa), R 3′ and R 2′ or R 4′ and/or R 6′ and R 5′ or R 7″ in the compounds of structural formula (III6), or R 3′ and R 2″ or R 4′ and/or R 6′ and R 5′ or R 7″ in the compounds of structural formula (IIIc) are taken together with the atoms to which they are bonded to form a 5- or 6-membered saturated or unsaturated ring which is optionally substituted with one or more of the same or different lower alkyl, benzo or pyrido groups,
with the proviso that at least one of R 2′ , R 4′ , R 5′ , R 7′ , R 5 or R 6 in the compounds of structural formula (IIIa), at least one of R 2′ , R 4′ , R 5′ , R 7″ , R 5 or R 6 in the compounds of structural formula (IIIb) or at least one of R 2″ , R 4′ , R 5′ , R 7″ , R 5 or R 6 in the compounds of structural formula (IIIc) comprises a group of the formula —Y—, wherein Y is selected from the group consisting of —C(O)—, —S(O) 2 —, —S— and —NH—.
2. The oligonucleotide of claim 1 , wherein the N-protected NH-rhodamine moiety is selected from the group consisting of structures having formulae (IIIa.1), (IIIa.2), (IIIb.1), (IIIb.2), (IIIc.1) and (IIIc.2):
3. The oligonucleotide of claim 1 , wherein the label moiety is linked to the 3′- or 5′-hydroxyl of the oligonucleotide.
4. The oligonucleotide of claim 1 in which the label moiety is linked to a nucleobase of the oligonucleotide.
5. The oligonucleotide of claim 1 , wherein the oligonucleotide is further labeled with a donor and/or acceptor moiety for the N-protected NH-rhodamine moiety.
6. The oligonucleotide of claim 1 , wherein the oligonucleotide is further labeled with a quencher moiety.
7. The oligonucleotide of claim 1 , wherein the oligonucleotide is further labeled with a minor groove binding moiety.
8. The oligonucleotide of claim 1 , wherein the N-protected NH-rhodamine moiety has at least one applicable feature selected from the group consisting of:
(i) each of R 4 and R 7 is chloro;
(ii) each of R 1′ and R 8′ is hydrogen;
(iii) R 1′ and R 2′ or R 7′ and R 8′ are taken together to form a benzo group;
(iv) each of R 2′ and R 7′ selected from the group consisting of hydrogen and a lower alkyl;
(v) R′ is R 3′ and R″ is R 6′ ; and
(vi) R′ is R 3′ , R″ is R 6′ , and R 3′ and R 6′ are taken together with a substituent group on an adjacent carbon atom to form a moiety selected from the group consisting of —CH 2 CH 2 —, —CH 2 CH 2 CH 2 —, —C(CH 3 ) 2 CH═C(CH 3 )—, —C(CH 3 ) 2 CH═CH—, —CH 2 —C(CH 3 ) 2 — and
9. The oligonucleotide of claim 1 , wherein R 10 is selected from the group consisting of methyl and trifluoromethyl.
10. The oligonucleotide of claim 1 , wherein the label moiety further comprises a donor moiety or an acceptor moiety for the N-protected NH-rhodamine moiety.
11. The oligonucleotide of claim 10 , wherein the label moiety further comprises a donor moiety for the N-protected NH-rhodamine moiety.
12. The oligonucleotide of claim 11 , wherein the donor moiety comprises an N-protected NH-rhodamine moiety or an O-protected fluorescein moiety.
13. The oligonucleotide of claim 12 , wherein the 2′-, 2″-, 4′-, 5′-, 7′-, 7″-, 5- or 6-position of the donor moiety is linked to the 2′-, 2″-, 4′-, 5′-, 7′-, 7″-, 5- or 6-position of the N-protected NH-rhodamine moiety.
14. The oligonucleotide of claim 13 , wherein the donor moiety and the N-protected NH-rhodamine moiety are linked in a head-to-head orientation.
15. The oligonucleotide of claim 13 , wherein the donor moiety and the N-protected NH-rhodamine moiety are linked in a head-to-tail orientation.
16. The oligonucleotide of claim 13 , wherein the donor moiety and the N-protected NH-rhodamine moiety are linked in a tail-to-tail orientation.
17. The oligonucleotide of claim 13 , wherein the donor moiety and the N-protected NH-rhodamine moiety are linked in a side-to-side orientation.
18. The oligonucleotide of claim 13 , wherein the donor moiety and the N-protected NH-rhodamine moiety are linked in a side-to-head orientation.
19. The oligonucleotide of claim 13 , wherein the donor moiety and the N-protected NH-rhodamine moiety are linked in a side-to-tail orientation.
20. The oligonucleotide of claim 13 , wherein the label moiety has structural formula (VI):
A-Z 1 -Sp-Z 2 -D (VI)
wherein A represents the N-protected NH-rhodamine moiety, D represents the donor moiety, Z 1 and Z 2 , which may be the same or different, represent portions of linkages provided by linking moieties comprising a functional group F z , and Sp represents a spacing moiety.
21. The oligonucleotide of claim 20 , wherein A is selected from the group consisting of moieties having structural formulae A.1, A.2, A.3, A.4, A.5 and A.6, and D is selected from the group consisting of moieties having structural formulae D.1, D.2, D.3, D.4, D.5 and D.6, or A is selected from the group consisting of moieties having structural formulae A.7, A.8, A.9, A.10, A.11 and A.12, and D is selected from the group consisting of moieties having structural formulae D.7, D.8, D.9, D.10, D.11 and D.12:
wherein:
R′ is selected from R 3′ and hydrogen;
R″ is selected from R 6′ and hydrogen;
R 9 is an acyl protecting group, optionally of the formula —C(O)R 10 , wherein R 10 is selected from the group consisting of hydrogen, —CX 3 , —CHX 2 , —CH 2 X, —CH 2 —OR d and phenyl optionally mono-substituted with a lower alkyl, —X, OR d , cyano or nitro group, wherein R d is selected from the group consisting of a lower alkyl, phenyl and pyridyl, and each X is a halo group;
each of R 1′ , R 2′ , R 2″ , R 4′ , R 4″ , R 5′ , R 5″ , R 7′ , R 7″ , and R 8′ , when taken alone, is independently selected from the group consisting of hydrogen, a lower alkyl, a (C6-C14) aryl, a (C7-C20) arylalkyl, a 5-14 membered heteroaryl, a 6-20 membered heteroarylalkyl, —R b and —(CH 2 ) x —R b , wherein x is an integer having the value between 1 and 10 and R b is selected from the group consisting of —X, —OH, —OR a , —SH, —SR a , —NH 2 , —NHR a , —NR c R c , —N + R c R c R c , perhalo lower alkyl, trihalomethyl, trifluoromethyl, —P(OH)O − , —P(OR a ) 2 , —P(OR a )O − , —P(O)(OH) 2 , —P(O)(OH)O − , —P(O)(O − ) 2 , —P(O)(OR a ) a , —P(O)(OR a )O − , —P(O)(OH)(OR a ), —OP(OH) 2 , —OP(OH)O − , —OP(OR a ) 2 , —OP(OR a )O − , —OP(O)(OH) 2 , —OP(O)(OH)O − , —OP(O)(O − ) 2 , —OP(O)(OR a ) 2 , —OP(O)(OR a )O − , —OP(O)(OR a )(OH), —S(O) 2 O − , —S(O) 2 OH, —S(O) 2 R a , —C(O)H, —C(O)R a , —C(S)X, —C(O)O − , —C(O)OH, —C(O)NH 2 , —C(O)NHR a , —C(O)NR c R c , —C(S)NH 2 , —C(O)NHR a , —C(O)NR c R c , —C(NH)NH 2 , —C(NH)NHR a , and —C(NH)NR c R c , wherein X is halo, each R a is independently selected from the group consisting of a lower alkyl, a (C6-C14) aryl, a (C7-C20) arylalkyl, a 5-14 membered heteroaryl and a 6-20 membered heteroarylalkyl, and each R c is independently an R a , or, alternatively, two R c bonded to the same nitrogen atom may be taken together with that nitrogen atom to form a 5- to 8-membered saturated or unsaturated ring that may optionally include one or more of the same or different ring heteroatoms selected from the group consisting of 0 N and S;
or, alternatively, R 1′ and R 2′ or R 7′ and R 8′ are taken together with the carbon atoms to which they are bonded to form an optionally substituted (C6-C14) aryl bridge and/or R 4′ and R 4″ and/or R 5′ and R 5″ are taken together with the carbon atoms to which they are bonded to form a benzo group; and
R 3′ and R 6′ , when taken alone, are each, independently of one another, selected from lower alkyl, (C6-C14) aryl, (C7-C20) arylalkyl, 5-14 membered heteroaryl and 6-20 membered heteroarylalkyl;
or alternatively, R 3′ and R 2′ or R 4′ and/or R 6′ and R 5′ or R 7′ in the compounds of structural formula A 1 , A 4 , A 7 or A 10 , R 3′ and R 2′ or R 4′ and/or R 6′ and R 5′ or R 7″ in the compounds of structural formula A 2 , A 5 , A 8 or A 11 , or R 3′ and R 2″ or R 4′ and/or R 6′ and R 5′ or R 7″ in the compounds of structural formula A 3 , A 6 , A 9 , or A 12 are taken together with the atoms to which they are bonded to form a 5- or 6-membered saturated or unsaturated ring that may optionally include from 1 to 4 additional heteroatoms (typically selected from O, N and S) and that is optionally substituted with one or more of the same or different lower alkyl, benzo or pyrido groups;
R 4 , R 5 , R 6 , and R 7 are each, independently of one another, selected from hydrogen, lower alkyl, (C6-C14) aryl, (C7-C20) arylalkyl, 6-14 membered heteroaryl, 7-20 membered heteroarylalkyl, —R b and —(CH 2 ) x —R b ;
E 1 is selected from the group consisting of —NHR 9 , —NR 3′ R 9 and —OR 9b ;
E 2 is selected from the group consisting of —NHR 9 , —NR 6′ R 9 and —OR 9b ;
R 9b is R 9 ;
each of Y 1a , Y 1b , Y 2a , Y 2b , Y 3a and Y 3b is independently selected from the group consisting of —O—, —S—, —NH—, —C(O—) and —S(O) 2 ,
with the proviso that when each of E 1 and E 2 is —OR 9b , then R 1′ and R 2′ and/or R 7′ and R 8′ are may only be taken together with the carbon atoms to which they are bound to form an optionally substituted (C6-C14) aryl bridge.
22. The oligonucleotide of claim 21 , wherein the moieties having the structural formulae A.1-A.12 and/or D.1-D.12 further include at least one applicable feature selected from the group consisting of:
(i) each of Y 1a , Y 2a and Y 3a is independently selected from the group consisting of —C(O)— and —S(O) 2 —;
(ii) each of Y 1b , Y 2b and Y 3b is —NH—;
(iii) each of R 4 and R 7 is chloro;
(iv) each of R 1′ and R 8′ is hydrogen;
(v) R 1′ and R 2′ or R 7′ and R 8′ are taken together to form a benzo group;
(vi) each of R 2′ and R 7′ is selected from the group consisting of hydrogen and a lower alkyl;
(vii) R′ is R 3′ and R″ is R 6′ ; and
(viii) R′ is R 3′ , R″ is R 6′ , and R 3′ and R 6′ are taken together with a substituent group on an adjacent carbon atom to form a group selected from —CH 2 CH 2 —, —CH 2 CH 2 CH 2 —, —C(CH 3 ) 2 CH═C(CH 3 )—, —C(CH 3 ) 2 CH═CH—, —CH 2 —C(CH 3 ) 2 — and
23. The oligonucleotide of claim 21 , wherein:
(i) each of Y 1a , Y 2a and Y 3a is NH—;
(ii) each of Y 1b , Y 2b and Y 3b is independently selected from the group consisting of —C(O)— and —S(O) 2 —;
(iii) Z 1 is selected from the group consisting of —C(O)— and —S(O) 2 —;
(iv) Z 2 is —NH—; and
(v) Sp is selected from the group consisting of —(CH 2 ) a —[(Ar) b —(CH 2 ) a ] c —, —(CH 2 ) a —[C≡C—(CH 2 ) a ] c —, —(CH 2 ) a —[C≡C—(Ar) b ] c —(CH 2 ) a —, —(CH 2 ) d —NH—C(O)—[(CH 2 ) a —(Ar)—(CH 2 ) a —C(O)—NH] c —(CH 2 ) d —, and —[CH 2 (CH 2 ) e O] f —CH 2 (CH 2 )—, wherein:
each a is independently an integer having the value between 0 and 4;
each b is independently an integer having the value between 1 and 2;
each c is independently an integer having the value between 1 and 5;
each d is independently an integer having the value between 1 and 10;
each e is independently an integer having the value between 1 and 4;
each f is independently an integer having the value between 1 and 10; and
each Ar is independently an optionally substituted monocyclic or polycyclic cycloalkylene, cycloheteroalkynene, arylene or heteroarylene group.
24. The oligonucleotide of claim 21 , wherein in the structures D.1-D.12, R 1′ and R 2′ and/or R 7′ and R 8′ are taken together with the carbon atoms to which they are bonded to form a benzo bridge.
25. The oligonucleotide of claim 21 , wherein each of E 1 and E 2 is —OR 9b .
26. The oligonucleotide of claim 25 , wherein R 9b is a group of the formula —C(O)R 10b , wherein R 10b is a lower alkyl.
27. The oligonucleotide of claim 26 , wherein R 10b is tert-butyl.
28. The oligonucleotide of claim 21 , wherein R 9 is a group of the formula —C(O)R 10 , wherein R 10 is selected from the group consisting of hydrogen, a lower alkyl, —CX 3 , —CHX 2 , —CH 2 X, —CH 2 —OR d and phenyl optionally mono-substituted with a lower alkyl, —X, —OR d , cyano or nitro group, wherein R d is selected from the group consisting of a lower alkyl, phenyl and pyridyl, and each X is a halo group.
29. The oligonucleotide of claim 28 , wherein R 10 is selected from the group consisting of methyl and trifluoromethyl.
30. The oligonucleotide of claim 1 , wherein the L of the reagent is selected from -Z-(CH 2 ) 3-6 —O—, -Z-(CH 2 ) a —[(Ar) b —(CH 2 ) a ] c —O—, -Z-(CH 2 ) a —[C≡C—(CH 2 ) a ] c —O—, -Z-(CH 2 ) a —[C≡C—(Ar) b ] c —(CH 2 ) a —O—, -Z-(CH 2 ) d —NH—C(O)—[(CH 2 ) a —(Ar)—(CH 2 ) a —C(O)—NH] c —(CH 2 ) d —O—, and -Z-[CH 2 (CH 2 ) e O] f —CH 2 (CH 2 ) e O—, wherein:
each Z represents, independently of the others, a portion of a linkage contributed by a functional group F z ;
each a represents, independently of the others, an integer ranging from 0 to 4;
each b represents, independently of the others, an integer ranging from 1 to 2;
each c represents, independently of the others, an integer ranging from 1 to 5;
each d represents, independently of the others, an integer ranging from 1 to 10;
each e represents, independently of the others, an integer ranging from 1 to 4;
each f represents, independently of the others, an integer ranging from 1 to 10; and
each Ar represents, independently of the others, an optionally substituted monocyclic or polycyclic cycloalkylene, cycloheteroalkynene, arylene or heteroarylene group.
31. The oligonucleotide of claim 30 , wherein each Ar of L, independently of the others, is a group derived cyclohexane, piperazine, benzene, napthalene, phenol, furan, pyridine, piperidine, imidazole, pyrrolidine or oxadizole.
32. The oligonucleotide of claim 1 , wherein the reagent further comprises a suitably protected synthesis handle comprising a reactive group selected from the group consisting of amino, hydroxyl, thiol and aldehyde and a protecting group configured a) to be removed to provide the reactive group for attachment of additional moieties during the course of synthesis of the oligonucleotide or b) to be stable during the course of synthesis of the oligonucleotide and be removed following synthesis of the oligonucleotide to provide the reactive group for attachment of additional moieties.
33. The oligonucleotide of claim 32 , wherein the reagent is a compound according to structural formula (VIII):
R e O-L-LM-L-PEP (VIII)
wherein R e represents an acid-labile protecting group, each L represents, independently of the other, an optional linker, LM represents the label moiety and PEP represents the phosphate ester precursor group.
34. The oligonucleotide of claim 32 , wherein the reagent is a compound according to structural formula (IX):
wherein R e represents an acid-labile protecting group.
35. The oligonucleotide of claim 34 , wherein the reagent is a compound according to structural formula (IX.1):
wherein -Z- represents a portion of a linkage contributed by a functional group F z , Sp 1 , Sp 2 and Sp 3 , which can be the same or different, each represent spacing moieties, and G represents CH, N, or a group comprising an arylene, phenylene, heteroarylene, lower cycloalkylene, cyclohexylene, and/or a lower cycloheteroalkylene.
36. The oligonucleotide of claim 35 , wherein Sp 1 , Sp 2 and Sp 3 are each, independently of one another, selected from an alkylene chain containing from 1 to 10 carbon atoms, —(CH 2 ) a —[(Ar) b —(CH 2 ) a ] c —, —(CH 2 ) a —[C≡C—(CH 2 ) a ] c —, —(CH 2 ) a —[C≡C—(Ar) b ] c —(CH 2 ) a —, —(CH 2 ) d —NH—C(O)—[(CH 2 ) a —(Ar)—(CH 2 ) a —C(O)—NH] c —(CH 2 ) d — and —[CH 2 (CH 2 ) e O] f —CH 2 (CH 2 )—, where each a represents, independently of the others, an integer ranging from 0 to 4;
each b represents, independently of the others, an integer ranging from 1 to 2;
each c represents, independently of the others, an integer ranging from 1 to 5;
each d represents, independently of the others, an integer ranging from 1 to 10;
each e represents, independently of the others, an integer ranging from 1 to 4;
each f represents, independently of the others, an integer ranging from 1 to 10; and Ar represents, independently of the others, an optionally substituted monocyclic or polycyclic cycloalkylene, cycloheteroalkynene, arylene or heteroarylene group.
37. The oligonucleotide of claim 32 , wherein the reagent is a compound according to structural formula (IX.2), (IX.3), (IX.4) or (IX.5):
wherein B represents a suitably protected nucleobase, L 2 represents a linker linking label moiety LM to nucleobase B and, in structure (IX.4), R 11 represents a protecting group; and
the nucleobase is selected from adenine, 7-deazaguanine, guanine, 7-deazaguanine, cytosine, uracil, thymine, inosine, xanthene and hypoxanthene.
38. The oligonucleotide of claim 37 , wherein B of the reagent is selected from A iBu , A Pac , C Ac , G iPr-Pac , T and U.
39. The oligonucleotide of claim 37 , wherein L 2 of the reagent is selected from —C≡C—CH 2 —NH—, —C≡C—C(O)—, —CH═CH—NH—, —CH═CH—C(O)—, —C≡C—CH 2 —NH—C(O)—(CH 2 ) 1-6 —NH—, —CH═CH—C(O)—NH—(CH 2 ) 1-6 —NH—C(O)—, —C═CH—CH 2 —O—CH 2 CH 2 —[O—CH 2 CH 2 ] 0-6 —NH—, —C≡C—C≡C—CH 2 —O—CH 2 CH 2 —[O—CH 2 CH 2 ] 0-6 —NH—, —C≡C—(Ar) 1-2 —C≡C—CH 2 —O—CH 2 CH 2 —[O—CH 2 CH 2 ] 0-6 —NH—, —C≡C—(Ar) 1-2 —O—CH 2 CH 2 —[O—CH 2 CH 2 ] 0-6 —NH— and —C≡C—(Ar) 1-2 —O—CH 2 CH 2 —[O—CH 2 CH 2 ] 0-6 —NH—, where Ar represents, independently of the others, an optionally substituted monocyclic or polycyclic cycloalkylene, cycloheteroalkynene, arylene or heteroarylene group.
40. The oligonucleotide of claim 1 , wherein the phosphate ester precursor group comprises a phosphoramidite group and an H-phosphonate group.
41. The oligonucleotide of claim 40 , wherein the phosphate ester precursor group comprises a phosphoramidite of the formula (P.1):
wherein:
R 20 is selected from a linear, branched or cyclic saturated or unsaturated alkyl containing from 1 to 10 carbon atoms, 2-cyanoethyl, an aryl containing from 6 to 10 ring carbon atoms and an arylalkyl containing from 6 to 10 ring carbon atoms and from 1 to 10 alkylene carbon atoms; and
R 21 and R 22 are each, independently of one another, selected from a linear, branched or cyclic, saturated or unsaturated alkyl containing from 1 to 10 carbon atoms, an aryl containing from 6 to 10 ring carbon atoms and an arylalkyl containing from 6 to 10 ring carbon atoms and from 1 to 10 alkylene carbon atoms, or, alternatively, R 21 and R 22 are taken together with the nitrogen atom to which they are bonded to form a saturated or unsaturated ring that contains from 5 to 6 ring atoms, one or two of which, in addition to the illustrated nitrogen atom, can be heteroatom selected from O, N and S.
42. The oligonucleotide of claim 40 , wherein R 20 is beta-cyanoethyl and R 21 and R 22 are each isopropyl.
43. The oligonucleotide of claim 32 , wherein the synthesis handle has the formula —OR e , where R e is an acid-labile protecting group.
44. The oligonucleotide of claim 43 wherein the acid-labile protecting group is selected from the group consisting of triphenylmethyl (trityl), 4-monomethoxytrityl, 4,4′-dimethoxytrityl, 4,4′,4″-trimethoxytrityl, bis (p-anisyl)phenylmethyl, naphthyldiphenylmethyl, p-(p′-bromophenacyloxy)phenyldiphenylmethyl, 9-anthryl, 9-(9-phenyl)xanthenyl and 9-(9-phenyl-10-oxo)anthryl.