METHOD FOR THE SYNTHESIS OF DHA
A method for preparing docosahexaenoic acid (DHA). The method comprises coupling a compound represented by Formula I with a compound represented by Formula II followed by partial hydrogenation to obtain a compound represented by Formula III. The compound represented by Formula III acts as a DHA precursor and thus can be hydrolysed to obtain DHA. Novel starting materials represented by Formula I and Formula II, and synthetic routes for preparing the same are also provided.
1 . A compound represented by Formula II:
or a pharmaceutically acceptable salt or stereoisomer thereof
2 - 3 . (canceled)
4 . A method for preparing a compound represented by Formula I
the method comprising the steps of:
(a) converting a propargyl alcohol to a compound represented by Formula IV:
(b) converting the compound represented by Formula IV to a compound represented by Formula V:
(c) converting propargyl alcohol to a compound represented by Formula VIa:
(d) converting the compound represented by Formula VIa to a compound represented by Formula VIIa:
(e) coupling the compound represented by Formula VIIa with the compound represented by Formula V to yield a compound represented by Formula VIIIa:
(f) converting the compound represented by Formula VIIIa to a compound represented by Formula IX:
and
(g) converting the compound represented by Formula IX to the compound represented by Formula I.
5 . A method as claimed in claim 4 , wherein step (a) comprises reacting said propargyl alcohol with an ethyl halide in the presence of a strong base and a polar aprotic solvent to obtain the compound represented by Formula IV.
6 . A method as claimed in claim 5 , wherein the ethyl halide is ethyl iodide, the strong base is n-BuLi, and the polar aprotic solvent is HMPA in THF.
7 . A method as claimed in claim 6 , wherein the step (a) is carried out at a temperature of between −78° C. to room temperature.
8 . A method as claimed in claim 4 , wherein the step (b) comprises reacting the compound represented by Formula IV with 4-Toluenesulfonyl chloride (TsCl) and a strong inorganic base to obtain the compound represented by Formula V.
9 . A method as claimed in claim 8 , wherein the strong inorganic base is potassium hydroxide (KOH).
10 . A method as claimed in claim 4 , wherein the step (c) comprises reacting propargyl alcohol with an alcohol protecting agent or group to obtain a compound represented by Formula VIa.
11 . A method as claimed in claim 10 , wherein the alcohol protecting agent or group is dihydropyran (DHP) and the DHP protection reaction produces a tetrahydropyranyl ether according to the compound represented by Formula VI:
12 . A method as claimed in claim 4 , wherein the step (d) comprises reacting the magnesium acetylide compound represented by Formula VIa with a propargyl halide in the presence of a catalyst to obtain the compound represented by Formula VIIa.
13 . A method as claimed in claim 12 wherein the propargyl halide is propargyl bromide and the catalyst is CuCl.
14 . A method as claimed in claim 4 , wherein the coupling reaction of step (e) is conducted in the presence of a polar aprotic solvent to obtain the compound represented by Formula VIIIa.
15 . A method as claimed in claim 14 , wherein the polar aprotic solvent is dimethylformamide (DMF).
16 . A method as claimed in claim 4 , wherein the step (f) comprises deprotecting the compound represented by Formula VIIIa in the presence of p-TSA/methanol.
17 . A method as claimed in claim 16 , wherein the deprotecting is carried out at a temperature of about 60° C.
18 . A method as claimed in claim 4 , wherein the step (g) comprises reacting the compound represented by Formula IX with a tosyl halide in pyridine to obtain the compound represented by Formula I.
19 . A method as claimed in claim 18 , wherein the tosyl halide is tosyl chloride.
20 . A method for preparing a compound represented by Formula II:
the method comprising the steps of:
(h) converting 2-Butyne-1,4-diol to a compound represented by Formula X:
(i) converting the compound represented by Formula X to a compound represented by Formula XI:
(j) converting the compound represented by Formula XI to a compound represented by Formula XII:
(k) converting the compound represented by Formula XII to a compound represented by Formula XIII:
and
(l) converting the compound represented by Formula XIII to the compound represented by Formula II.
21 . A method as claimed in claim 20 , wherein the step (a) comprises reacting the 2-butyne-1,4-diol with tosyl chloride and pyridine in an organic solvent to obtain the compound represented by Formula X.
22 . A method as claimed in claim 21 , wherein the organic solvent is dichloromethane.
23 . A method as claimed in claim 20 , wherein the step (b) comprises reacting the compound represented by Formula X with trimethylsilyl acetylene to produce the compound represented by Formula XI.
24 . A method as claimed in claim 20 , wherein the step (c) comprises tosylation of the compound represented by Formula XI to produce the compound represented by Formula XII.
25 . A method as claimed in claim 24 , wherein the tosylation reaction is carried out by reacting the compound represented by Formula XI with p-toluenesulfonic acid.
26 . A method as claimed in claim 20 , wherein the step (d) comprises reacting the compound represented by Formula XII with methyl-4-pentynoate to produce the compound represented by Formula XIII.
27 . A method as claimed in claim 20 , wherein the step (e) comprises deprotecting the compound represented by Formula XIII with tetra-n-butylammonium fluoride (TBAF) in a solvent to produce the compound represented by Formula II.
28 . A method as claimed in claim 27 , wherein the solvent is dichloromethane.
29 . A method of preparing DHA:
the method comprising the steps of:
(m) coupling a compound represented by Formula I:
with a compound represented by Formula II:
to obtain a compound represented by Formula III:
(n) partially hydrogenating the compound represented by Formula III to produce a compound represented by Formula XIV:
and
(o) hydrolysing the compound represented by Formula XIV to produce DHA,
or, the method comprising the steps of:
(a′) partially hydrogenating a compound represented by Formula III:
to produce a compound represented by Formula XIV:
(b′) hydrolysing the compound represented by Formula XIV to produce DHA.
30 . A method as claimed in claim 29 , wherein the step (a) is conducted in the presence of CuI, NaI and K 2 CO 3 in a polar aprotic solvent.
31 . A method as claimed in claim 30 , wherein the polar aprotic solvent is dimethylformamide (DMF).
32 . A method as claimed in claim 29 , wherein the step (b) or (a′) is conducted in the presence of Lindlar's catalyst.
33 - 34 . (canceled)