Methods for the synthesis of 13C labeled plasmalogen

1. A process of preparing a compound represented by Formula A

wherein the compound is 13 C labeled at one or more carbon atoms marked with an asterisk, R 1 * and R 2 * are the same or different 13 C labeled saturated, unsaturated, or polyunsaturated C 1 -C 28 hydrocarbon chains comprising at least one 13 C labeled carbon atom, and optionally derived from fatty acids; and R 3 is hydrogen or a C 1 -C 3 alkyl group, the process comprising:

a) protecting the diol present in 13 C labeled glycerol of Formula 1:

by reaction with dimethoxypropane to obtain a solketal represented by the compound of Formula 2:

b) coupling the primary alcohol in the compound of Formula 2 with an allyl halide to obtain a compound represented by Formula 3:

c) deprotecting the ketal present in the compound represented by Formula 3 to obtain a compound represented by Formula 4

d) protecting the diol present in the compound represented by Formula 4 using a protecting agent to obtain a compound represented by Formula (v):

e) reacting a 13 C labeled haloalkane as represented by X—R 1 * with the compound represented by Formula (v) to obtain a compound represented by Formula (vi)

wherein R 1 * is as defined above and X is a halogen,

f) deprotecting the ether groups present in the compound represented by Formula (vi) to obtain a compound represented by Formula 7

g) protecting the primary alcohol present in the compound represented by Formula 7 using a protecting agent to obtain a compound represented by Formula (viii)

h) esterifying a 13 C labeled fatty acid as represented by R 2 *—COOH to the compound represented by Formula (viii) to obtain a compound represented by Formula (ix):

wherein R 2 * is as defined above,

i) deprotecting the ether present in the compound represented by Formula (ix) to yield a compound represented by Formula 10

and

j) reacting POCl 3 with the compound represented by Formula 10, ethanolamine, and triethanolamine (TEA) to yield the compound represented by Formula A.

2. The process as claimed in claim 1 wherein R 1 *, R 2 * or both R 1 * and R 2 * are C 1 -C 28 alkyl chains comprising up to 6 double bonds.

3. The process as claimed in claim 1 wherein R 1 * is a C 1 -C 20 alkyl group.

4. The process as claimed in claim 1 wherein R 2 * is a C2-C28 alkenyl group with 1 to 6 double bonds.

5. The process as claimed in claim 1 wherein R 3 is hydrogen.

6. The process as claimed in claim 1 wherein the allyl halide is allyl bromide.

7. The process as claimed in claim 1 wherein the diol present in the compound represented by Formula 4 is protected with a tert-butyldimethylsilyl (TBS) group.

8. The process as claimed in claim 1 wherein X in XR 1 * is Cl, Br, F or I.

9. The process as claimed in claim 8 wherein X in XR 1 * is I.

10. The process as claimed in claim 1 wherein the primary alcohol present in the compound represented by Formula 7 is protected with a tert-butyldimethylsilyl (TBS) group.

11. The process as claimed in claim 1 wherein the 13 C labeled haloalkane as represented by X—R 1 * in step (e) is 13 C-iodotridecane.

12. The process as claimed in claim 11 wherein the is 13 C -iodotridecane is chemically synthesized.

13. The process as claimed in claim 1 wherein the 13 C labeled fatty acid as represented by R 2 *—COOH in step (h) is 13 C-docosahexaenoic acid ( 13 C-DHA).

14. The process as claimed in claim 13 wherein the 13 C-DHA is chemically synthesized.

15. The process as claimed in claim 1 , wherein the protecting reaction of step (a) is carried out in the presence of dimethoxy propane and p-toluenesulfonic acid (PTSA).

16. The process as claimed in claim 15 , wherein the protecting reaction of step (a) is carried out at about room temperature.

17. The process as claimed in claim 1 , wherein the coupling reaction of step (b) is carried out in the presence of NaH, tetrahydrofuran (THF) and allyl bromide.

18. The process as claimed in claim 17 , wherein the coupling reaction of step (b) is carried out at a temperature of between about 0° C. to about room temperature.

19. The process as claimed in claim 1 , wherein the deprotecting reaction of step (c) is conducted under acidic conditions in the presence of HCl.

20. The process as claimed in claim 19 , wherein the deprotecting reaction of step (c) is carried out at a temperature of about 80° C.

21. The process as claimed in claim 1 , wherein the protection reaction of step (d) comprises reacting the compound represented by Formula 4 with a tert-butyldimethylsilyl chloride (TBDMSCl) in the presence of DMF and Imidazole.

22. The process as claimed in claim 21 , wherein the protection reaction of step (d) is carried out at a temperature of between about 0° C. to about room temperature.

23. The process as claimed in claim 1 , wherein the step (e) comprises reacting a haloalkane dissolved in THF with the compound represented by Formula (v) in the presence of tetrahydrofuran (THF) and Sec-BuLi.

24. The process as claimed in claim 23 , wherein the step (e) is carried out at a temperature of between about −78° C. to about room temperature.

25. The process as claimed in claim 24 , wherein the haloalkane is 13 C-iodotridecane.

26. The process as claimed in claim 25 , wherein the compound formed in step (e) is an α alkylated compound as represented by Formula (vi).

27. The process as claimed in claim 1 , wherein the deprotection reaction of step (f) is carried out in presence of tetrahydrofuran (THF) and tetra-n-butylammonium fluoride (TBAF).

28. The process as claimed in claim 27 , wherein the deprotection reaction of step (f) is carried out at a temperature of between about 0° C. to about room temperature.

29. The process as claimed in claim 1 , wherein the protection reaction of step (g) comprises reacting tert-butyldimethylsilyl chloride (TBDMSCl) with the compound represented by Formula 7 in the presence of dichloromethane (DCM), DEA and 4-dimethylaminopyridine (DMAP).

30. The process as claimed in claim 29 , wherein the protection reaction of step (g) is carried out at a temperature of between about 0° C. to about room temperature.

31. The process as claimed in claim 1 , wherein the esterification reaction of step (h) is carried out in the presence of dichloromethane (DCM), 1-ethyl-3-(3-dimethyllaminopropyl) carbodiimide hydrochloride (EDC.HCl) and 4-dimethylaminopyridine (DMAP).

32. The process as claimed in claim 31 , wherein the esterification reaction of step (h) is carried out at a temperature of between about 0° C. to about room temperature.

33. The process as claimed in claim 32 , wherein the 13 C labeled fatty acid is 13 C-docosahexaenoic acid ( 13 C-DHA).

34. The process as claimed in claim 1 , wherein the deprotection reaction of step (i) is carried out in the presence of tetrahydrofuran (THF), AcOH and tetra-n-butylammonium fluoride (TBAF).

35. The process as claimed in claim 34 , wherein the deprotection reaction of step (i) is carried out at a temperature of between about 0° C. to about room temperature.

36. The process as claimed in claim 1 , wherein the step (j) comprises:

a) reacting POCl 3 with the compound represented by Formula 10 dissolved in trichloroethylene in the presence of hexane and triethanolamine (TEA) to obtain a crude material;

b) dissolving the crude material in tetrahydrofuran (THF) forming a reaction mixture; and

c) adding ethanolamine and TEA in THF to the reaction mixture to yield a compound represented by Formula A.

37. The process as claimed in claim 1 , wherein the step (j) is carried out at a temperature of between about 0° C. to about room temperature.

38. The process as claimed in claim 1 , wherein the compound represented by Formula A is:

39. A process of converting a compound represented by Formula A:

wherein the compound is 13 C labeled at one or more carbon atoms marked with an asterisk, R 1 * and R 2 * are the same or different 13 C labeled saturated, unsaturated, or polyunsaturated C 1 -C 28 hydrocarbon chains comprising at least one 13 C labeled carbon atom, and optionally derived from fatty acids; and R 3 is hydrogen or a C 1 -C 3 alkyl group, the process comprising converting the compound represented by Formula A to a compound represented by Formula B:

the conversion process being carried out in the presence of tetrahydrofuran (THF) and H 2 O.

40. The process as claimed in claim 39 , wherein the compound represented by Formula A is

41. The compound of Formula A:

wherein the compound is 13 C labeled at one or more carbon atoms marked with an asterisk, R 1 * and R 2 * are the same or different 13 C labeled saturated, unsaturated, or polyunsaturated C 1 -C 28 hydrocarbon chains comprising at least one 13 C labeled carbon atom, and optionally derived from fatty acids; and R 3 is hydrogen or a C 1 -C 3 alkyl group, prepared by the process as claimed in claim 1 .

42. The compound of Formula B:

wherein the compound is 13 C labeled at one or more carbon atoms marked with an asterisk, R 1 * and R 2 * are the same or different 13 C labeled saturated, unsaturated, or polyunsaturated C 1 -C 28 hydrocarbon chains comprising at least one 13 C labeled carbon atom, and optionally derived from fatty acids; and R 3 is hydrogen or a C 1 -C 3 alkyl group, the compound of Formula B being prepared by the process of claim 39 .

43. A reference marker for use in metabolic studies comprising a compound of Formula B:

wherein the compound is 13 C labeled at one or more carbon atoms marked with an asterisk, R 1 * and R 2 * are the same or different 13 C labeled saturated, unsaturated, or polyunsaturated C 1 -C 28 hydrocarbon chains comprising at least one 13 C labeled carbon atom, and optionally derived from fatty acids; and R 3 is hydrogen or a C 1 -C 3 alkyl group.

44. The reference marker as claimed in claim 43 , wherein the compound represented by Formula B is: