Chiral control

1. A chirally controlled oligonucleotide composition comprising a plurality of oligonucleotides of at least one type, wherein each type is defined by:

1) base sequence;

2) pattern of backbone linkages;

3) pattern of backbone chiral centers; and

4) pattern of backbone X-moieties (—X-L-R 1 );

wherein:

the oligonucleotides of the at least one type comprise one or more phosphorothioate triester internucleotidic linkages and one or more phosphate diester linkage;

the oligonucleotides of the at least one type comprise at least two consecutive modified internucleotidic linkages; and

oligonucleotides of the at least one oligonucleotide type comprise one or more modified internucleotidic linkages independently having the structure of formula (I):

wherein:

P* is an asymmetric phosphorus atom and is either Rp or Sp;

W is O, S or Se;

each of X, Y and Z is independently —O—, —S—, —N(-L-R 1 )—, or L;

L is a covalent bond or an optionally substituted, linear or branched C 1 -C 50 alkylene, wherein one or more methylene units of L are optionally and independently replaced by an optionally substituted C 1 -C 6 alkylene, C 1 -C 6 alkenylene, —C≡C—, —C(R′) 2 —, -Cy-, —O—, —S—, —S—S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O) 2 —, —S(O) 2 N(R′)—, —N(R′)S(O) 2 —, —SC(O)—, —C(O)S—, —OC(O)—, or —C(O)O—;

R 1 is halogen, R, or an optionally substituted C 1 -C 10 aliphatic wherein one or more methylene units are optionally and independently replaced by an optionally substituted C 1 -C 6 alkylene, C 1 -C 6 alkenylene, —C≡C—, —C(R′) 2 —, -Cy-, —O—, —S—, —S—S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O) 2 —, —S(O) 2 N(R′)—, —N(R′)S(O) 2 —, —SC(O)—, —C(O)S—, —OC(O)—, or —C(O)O—;

each R′ is independently —R, —C(O)R, —CO 2 R, or —SO 2 R, or:

two R′ on the same nitrogen are taken together with their intervening atoms to form an optionally substituted heterocyclic or heteroaryl ring, or

two R′ on the same carbon are taken together with their intervening atoms to form an optionally substituted aryl, carbocyclic, heterocyclic, or heteroaryl ring;

-Cy- is an optionally substituted bivalent ring selected from phenylene, carbocyclylene, arylene, heteroarylene, or heterocyclylene;

each R is independently hydrogen, or an optionally substituted group selected from C 1 -C 6 aliphatic, phenyl, carbocyclyl, aryl, heteroaryl, or heterocyclyl; and

each

independently represents a connection to a nucleoside.

2. The composition of claim 1 , wherein the oligonucleotides are cleaved from a solid support.

3. The composition of claim 2 , wherein the oligonucleotides comprise one or more modified internucleotide linkages independently having the structure of formula I-b:

wherein:

P* is an asymmetric phosphorus atom and is either Rp or Sp;

X is —S—;

L is a covalent bond or an optionally substituted, linear or branched C 1 -C 50 alkylene, wherein one or more methylene units of L are optionally and independently replaced by an optionally substituted C 1 -C 6 alkylene, C 1 -C 6 alkenylene, —C≡C—, —C(R′) 2 —, -Cy-, —O—, —S—, —S—S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O) 2 —, —S(O) 2 N(R′)—, —N(R′)S(O) 2 —, —SC(O)—, —C(O)S—, —OC(O)—, or —C(O)O—;

R 1 is halogen, R, or an optionally substituted C 1 -C 10 aliphatic wherein one or more methylene units are optionally and independently replaced by an optionally substituted C 1 -C 6 alkylene, C 1 -C 6 alkenylene, —C≡C—, —C(R′) 2 —, -Cy-, —O—, —S—, —S—S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O) 2 —, —S(O) 2 N(R′)—, —N(R′)S(O) 2 —, —SC(O)—, —C(O)S—, —OC(O)—, or —C(O)O—;

each R′ is independently —R, —C(O)R, —CO 2 R, or —SO 2 R, or:

two R′ on the same nitrogen are taken together with their intervening atoms to form an optionally substituted heterocyclic or heteroaryl ring, or

two R′ on the same carbon are taken together with their intervening atoms to form an optionally substituted aryl, carbocyclic, heterocyclic, or heteroaryl ring;

-Cy- is an optionally substituted bivalent ring selected from phenylene, carbocyclylene, arylene, heteroarylene, or heterocyclylene;

each R is independently hydrogen, or an optionally substituted group selected from C 1 -C 6 aliphatic, phenyl, carbocyclyl, aryl, heteroaryl, or heterocyclyl; and

each

independently represents a connection to a nucleoside.

4. The composition of claim 3 , wherein the oligonucleotides are at least 15 nucleotide units in length.

5. The composition of claim 3 , wherein the composition contains predetermined levels of at least two oligonucleotide types.

6. A chirally controlled oligonucleotide comprising one or more modified internucleotide linkages independently having the structure of formula I:

wherein:

P* is an asymmetric phosphorus atom and is either Rp or Sp;

W is O, S or Se;

each of X, Y and Z is independently —O—, —S—, —N(-L-R 1 )—, or L;

L is a covalent bond or an optionally substituted, linear or branched C 1 -C 50 alkylene, wherein one or more methylene units of L are optionally and independently replaced by an optionally substituted C 1 -C 6 alkylene, C 1 -C 6 alkenylene, —C≡C—, —C(R′) 2 —, -Cy-, —O—, —S—, —S—S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O) 2 —, —S(O) 2 N(R′)—, —N(R′)S(O) 2 —, —SC(O)—, —C(O)S—, —OC(O)—, or —C(O)O—;

R 1 is halogen, R, or an optionally substituted C 1 -C 10 aliphatic wherein one or more methylene units are optionally and independently replaced by an optionally substituted C 1 -C 6 alkylene, C 1 -C 6 alkenylene, —C≡C—, —C(R′) 2 —, -Cy-, —O—, —S—, —S—S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O) 2 —, —S(O) 2 N(R′)—, —N(R′)S(O) 2 —, —SC(O)—, —C(O)S—, —OC(O)—, or —C(O)O—;

each R′ is independently —R, —C(O)R, —CO 2 R, or —SO 2 R, or:

two R′ on the same nitrogen are taken together with their intervening atoms to form an optionally substituted heterocyclic or heteroaryl ring, or

two R′ on the same carbon are taken together with their intervening atoms to form an optionally substituted aryl, carbocyclic, heterocyclic, or heteroaryl ring;

-Cy- is an optionally substituted bivalent ring selected from phenylene, carbocyclylene, arylene, heteroarylene, or heterocyclylene;

each R is independently hydrogen, or an optionally substituted group selected from C 1 -C 6 aliphatic, phenyl, carbocyclyl, aryl, heteroaryl, or heterocyclyl; and

each

independently represents a connection to a nucleoside;

the oligonucleotide comprises one or more phosphorothioate triester internucleotidic linkages and one or more phosphate diester linkage; and

the oligonucleotide comprises at least two consecutive modified internucleotidic linkages.

7. The chirally controlled oligonucleotide of claim 6 , comprising at least 5, at least 6, or at least 7 consecutive modified internucleotidic linkages, and at least one of the consecutive modified internucleotidic linkages is not a phosphorothioate diester linkage.

8. The chirally controlled oligonucleotide of claim 7 , wherein the chirally controlled oligonucleotide is at least 15 nucleotide units in length.

9. A pharmaceutical composition comprising a therapeutically effective amount of a composition of claim 1 and a pharmaceutically acceptable excipient.

10. The composition of claim 4 , wherein the oligonucleotides comprise one or more modified internucleotide linkages independently having the structure of formula I-b wherein -L-R 1 is not hydrogen.

11. The composition of claim 3 , wherein the oligonucleotides comprise one or more modified nucleobases.

12. The composition of claim 3 , wherein the oligonucleotides comprise one or more modified sugars.

13. The composition of claim 4 , wherein the oligonucleotides comprise one or more modified sugars.

14. The composition of claim 10 , wherein the oligonucleotides comprise one or more modified sugars.

15. The composition of claim 3 , wherein the oligonucleotides comprise one or more 2′-modified sugars.

16. The composition of claim 4 , wherein the oligonucleotides comprise one or more 2′-modified sugars.

17. The composition of claim 10 , wherein the oligonucleotides comprise one or more 2′-modified sugars.

18. The composition of claim 3 , wherein the oligonucleotides comprise one or more 2′-F modifications.

19. The composition of claim 4 , wherein the oligonucleotides comprise one or more 2′-F modifications.

20. The composition of claim 10 , wherein the oligonucleotides comprise one or more 2′-F modifications.

21. The composition of claim 3 , wherein the oligonucleotides comprise one or more 2′-OR′ modifications, wherein R′ is independently optionally substituted C 1 -C 6 aliphatic.

22. The composition of claim 4 , wherein the oligonucleotides comprise one or more 2′-OR′ modifications, wherein R′ is independently optionally substituted C 1 -C 6 aliphatic.

23. The composition of claim 10 , wherein the oligonucleotides comprise one or more 2′-OR′ modifications, wherein R′ is independently optionally substituted C 1 -C 6 aliphatic.

24. The composition of claim 3 , wherein the oligonucleotides comprise one or more locked nucleic acid moieties.

25. The composition of claim 4 , wherein the oligonucleotides comprise one or more locked nucleic acid moieties.

26. The composition of claim 10 , wherein the oligonucleotides comprise one or more locked nucleic acid moieties.

27. The composition of claim 4 , wherein the oligonucleotides comprise at least one Rp modified internucleotidic linkage and at least one Sp modified internucleotidic linkage.

28. The composition of claim 27 , wherein the oligonucleotides comprise at least one phosphorothioate diester linkage.

29. The composition of claim 28 , wherein the oligonucleotides comprise one or more modified nucleobases.

30. The composition of claim 28 , wherein the oligonucleotides comprise one or more modified sugars.

31. The composition of claim 28 , wherein the oligonucleotides comprise one or more 2′-modified sugars.

32. The composition of claim 28 , wherein the oligonucleotides comprise one or more 2′-F modifications.

33. The composition of claim 28 , wherein the oligonucleotides comprise one or more 2′-OR′ modifications, wherein R′ is independently optionally substituted C 1 -C 6 aliphatic.

34. The composition of claim 28 , wherein the oligonucleotides comprise one or more locked nucleic acid moieties.

35. The composition of claim 1 , wherein oligonucleotides of at least one oligonucleotide type comprise at least two individual internucleotidic linkages having different P-modifications relative to one another.

36. The composition of claim 35 , wherein the oligonucleotides are cleaved from a solid support.

37. The composition of claim 36 , wherein the oligonucleotides comprise one or more modified nucleobases.

38. The composition of claim 36 , wherein the oligonucleotides comprise one or more modified sugars.

39. The composition of claim 36 , wherein the oligonucleotides comprise one or more 2′-modified sugars.

40. The composition of claim 36 , wherein the oligonucleotides comprise one or more 2′-F modifications.

41. The composition of claim 36 , wherein the oligonucleotides comprise one or more 2′-OR′ modifications, wherein R′ is independently optionally substituted C 1 -C 6 aliphatic.

42. The composition of claim 36 , wherein the oligonucleotides comprise one or more locked nucleic acid moieties.

43. A chirally controlled oligonucleotide composition comprising a plurality of oligonucleotides of the same type, wherein the type is defined by:

1) base sequence;

2) pattern of backbone linkages;

3) pattern of backbone chiral centers; and

4) pattern of backbone X-moieties (—X-L-R 1 );

wherein:

the oligonucleotides of the same type comprise one or more phosphorothioate triester internucleotidic linkages and one or more phosphate diester linkage;

the oligonucleotides of the same type comprise at least two consecutive modified internucleotidic linkages; and

oligonucleotides of the same type comprise one or more modified internucleotidic linkages independently having the structure of formula (I):

wherein:

P* is an asymmetric phosphorus atom and is either Rp or Sp;

W is O, S or Se;

each of X, Y and Z is independently —O—, —S—, —N(-L-R 1 )—, or L;

L is a covalent bond or an optionally substituted, linear or branched C 1 -C 50 alkylene, wherein one or more methylene units of L are optionally and independently replaced by an optionally substituted C 1 -C 6 alkylene, C 1 -C 6 alkenylene, —C≡C—, —C(R′) 2 —, -Cy-, —O—, —S—, —S—S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O) 2 —, —S(O) 2 N(R′)—, —N(R′)S(O) 2 —, —SC(O)—, —C(O)S—, —OC(O)—, or —C(O)O—;

R 1 is halogen, R, or an optionally substituted C 1 -C 10 aliphatic wherein one or more methylene units are optionally and independently replaced by an optionally substituted C 1 -C 6 alkylene, C 1 -C 6 alkenylene, —C≡C—, —C(R′) 2 —, -Cy-, —O—, —S—, —S—S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O) 2 —, —S(O) 2 N(R′)—, —N(R′)S(O) 2 —, —SC(O)—, —C(O)S—, —OC(O)—, or —C(O)O—;

each R′ is independently —R, —C(O)R, —CO 2 R, or —SO 2 R, or:

two R′ on the same nitrogen are taken together with their intervening atoms to form an optionally substituted heterocyclic or heteroaryl ring, or

two R′ on the same carbon are taken together with their intervening atoms to form an optionally substituted aryl, carbocyclic, heterocyclic, or heteroaryl ring;

-Cy- is an optionally substituted bivalent ring selected from phenylene, carbocyclylene, arylene, heteroarylene, or heterocyclylene;

each R is independently hydrogen, or an optionally substituted group selected from C 1 -C 6 aliphatic, phenyl, carbocyclyl, aryl, heteroaryl, or heterocyclyl; and

each

independently represents a connection to a nucleoside.

44. The composition of claim 43 , wherein the oligonucleotides comprise one or more modified internucleotide linkages independently having the structure of formula I-b:

wherein:

P* is an asymmetric phosphorus atom and is either Rp or Sp;

X is —S—;

L is a covalent bond or an optionally substituted, linear or branched C 1 -C 50 alkylene, wherein one or more methylene units of L are optionally and independently replaced by an optionally substituted C 1 -C 6 alkylene, C 1 -C 6 alkenylene, —C≡C—, —C(R′) 2 —, -Cy-, —O—, —S—, —S—S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O) 2 —, —S(O) 2 N(R′)—, —N(R′)S(O) 2 —, —SC(O)—, —C(O)S—, —OC(O)—, or —C(O)O—;

R 1 is halogen, R, or an optionally substituted C 1 -C 10 aliphatic wherein one or more methylene units are optionally and independently replaced by an optionally substituted C 1 -C 6 alkylene, C 1 -C 6 alkenylene, —C≡C—, —C(R′) 2 —, -Cy-, —O—, —S—, —S—S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O) 2 —, —S(O) 2 N(R′)—, —N(R′)S(O) 2 —, —SC(O)—, —C(O)S—, —OC(O)—, or —C(O)O—;

each R′ is independently —R, —C(O)R, —CO 2 R, or —SO 2 R, or:

two R′ on the same nitrogen are taken together with their intervening atoms to form an optionally substituted heterocyclic or heteroaryl ring, or

two R′ on the same carbon are taken together with their intervening atoms to form an optionally substituted aryl, carbocyclic, heterocyclic, or heteroaryl ring;

-Cy- is an optionally substituted bivalent ring selected from phenylene, carbocyclylene, arylene, heteroarylene, or heterocyclylene;

each R is independently hydrogen, or an optionally substituted group selected from C 1 -C 6 aliphatic, phenyl, carbocyclyl, aryl, heteroaryl, or heterocyclyl; and

each

independently represents a connection to a nucleoside.

45. The composition of claim 44 , wherein the oligonucleotides are at least 15 nucleotide units in length.

46. The composition of claim 45 , wherein the oligonucleotides are cleaved from a solid support.

47. The composition of claim 46 , wherein the oligonucleotides comprise-one or more modified nucleobases.

48. The composition of claim 46 , wherein the oligonucleotides comprise one or more modified sugars.