Method for the synthesis of phospholipid ethers
Disclosed are improved methods for the synthesis of phospholipid ether analogs and alkyl phosphocholine analogs. The methods allow greater versatility of the reactants used and greater ease in synthesizing alkyl chains of varying length while affording reaction temperatures at room temperature or below. The methods disclosed herein provide reactants and conditions using alkyl halides and organozinc reagents and do not utilize Gringard reactions thus, allowing greater ease of their separation and purity of products. The PLE compounds synthesized by the methods disclosed herein can also be used for synthesizing high specific activity phospholipid ether (PLE) analogs, for use in treatment and diagnosis of cancer.
1. A method of synthesizing a phospholipid ether (PLE) analog or an alkyl phosphocholine (APC) analog comprising by the cross-coupling of an organo zinc reagent with an alkyl halide reagent comprising the steps of:
a) coupling an alkyl organo metallic with an alkyl iodide in the presence of an Ni(II)-Pybox or Pd-PEPPSI catalyst;
b) attaching an iodophenyl group in the presence of an Ni(II)-Pybox catalyst to yield an iodophenyl alcohol; and
c) converting the iodophenyl alcohol to an iodophenyl phosphocholine using an ethylene chlorophosphate and trimethylamine;
wherein an alkyl phosphocholine or a phospholipid ether is synthesized.
2. The method of claim 1 , wherein the phospholipid ether analog has the formula:
where X is selected from the group consisting of radioactive isotopes of halogen; n is an integer between 8 and 30; and Y is selected from the group comprising NH 2 , NR 2 , and NR 3 , wherein R is an alkyl or arylalkyl substituent or:
where X is a radioactive isotope of halogen; n is an integer between 8 and 30; Y is selected from the group consisting of H, OH, COOH, COOR and OR, and Z is selected from the group consisting of NH 2 , NR 2 , and NR 3 , wherein R is an alkyl or arylalkyl substituent.
3. The PLE analog of claim 2 , wherein X is selected from the group of radioactive halogen isotopes consisting of 18 F, 36 Cl, 76 Br, 77 Br, 82 Br, 122 I, 123 I, 124 I, 125 I, 131 I, 211 At and combinations thereof.
4. The method of claim 1 , wherein an alkyl chain elongation process is: IPhC 1 +C 11 +C 6 =IPhC 18 , C 6 +C 11 +IPhC 1 =IPhC 18 or C 16 +IPhC 2 =IPhC 18 .
5. The method of claim 1 , wherein in step b, the catalyst is:
wherein R is selected from the group consisting of: i-Pr: i-Pr-Pybox; s-Bu: s-Bu-Pybox; Ph: Ph-Pybox; H: Pybox; BnCH 2 : BnCH 2 -Pybox; or
6. The method of claim 1 , further including synthesizing a high specific activity phospholipid ether (PLE) analog, comprising the steps of:
(a) coupling an ester of diboron with a PLE or APC analog in the presence of a catalyst to result in a boronic acid or ester PLE or APC analog;
(b) optionally, esterifying the boronic acid of the PLE analog with 1,2- or 1,3-diols to result in the boronic esters of PLE or APC analog to step (a); and
(c) optionally, reacting the boronic acid or ester of PLE or APC analog of step (a) or (b) with sodium radiohalide, in the presence of an oxidant to result in a high specific activity radiohalogenated PLE or APC analog.
7. The method of claim 5 , wherein the coupling reaction of step (a) is carried out with methanol as a solvent at temperature of about 15-70° C. in the presence of a Pd catalyst.
8. The method of claim 6 , wherein the catalyst has the formula:
9. The method of claim 5 , wherein in step (c) the oxidant is selected from the group consisting of: dichloramine-T, chloramine-B, dichloramine-B, iodogen, iodogen coated tubes, iodobeads, N-chlorosuccinimide, hydrogen peroxide, peracetic acid, m-chloro-perbenzoic acid and peroxidase.
10. The method of claim 5 , wherein the synthesis of the high specific activity PLE analog proceeds through an intermediate having the structure:
where M is selected from the group consisting of Li, Na, K, Cs and Rb.