Nordihydroguaiartic derivatives for use in treatment of tumors

1. A method of synthesizing a chloride salt of a compound of the formula

wherein R 1 , R 2 , R 3 , and R 4 are identical and represent an amino acid residue or N,N-dimethyl substituted amino acid residue comprising the steps of:

(a) combining nordihydroguaiaretic acid (NDGA) and an amino acid or N,N-dimethyl substituted amino acid; and

(b) adding hydrogen chloride;

wherein these steps are performed under conditions to produce a chloride salt of a derivative of NDGA.

2. The method of claim 1 , wherein the step of combining NDGA and an amino acid or N,N-dimethyl substituted amino acid is performed in a dichloromethane solution.

3. The method of claim 1 , wherein the amino acid is selected from the group consisting of: alanine, arginine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, 5-hydroxylysine, 4-hydroxyproline, thyroxine, 3-methylhistidine, ε-N-methyllysine, ε-N,N,N-trimethyllysine, aminoadipic acid, γ-carboxyglutamic acid, phosphoserine, phosphothreonine, phosphotyrosine, N-methylarginine, and N-acetyllysine.

4. The method of claim 1 , wherein the N.N-dimethyl substituted amino acid is N,N-dimethylglycine.

5. The method of claim 2 , further comprising, before step (b), the step of:

adding dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) to the dichloromethane solution to form a reaction mixture.

6. The method of claim 5 , further comprising, before step (b), the step of stirring the reaction mixture.

7. The method of claim 5 , further comprising, before step (b), the step of filtering the reaction mixture to produce a filtered solution.

8. The method of claim 7 , further comprising, before step (b), the step of concentrating the filtered solution.

9. The method of claim 5 , further comprising, before step (b), the step of adding acetone, whereby a precipitate is produced after step (b).

10. The method of claim 7 , further comprising, before step (b), the step of adding acetone to the filtered solution, whereby a precipitate is produced after step (b).

11. The method of claim 8 , further comprising, before step (b), the step of adding acetone to the filtered solution, whereby a precipitate is produced after step (b).

12. The method of claim 1 , wherein the hydrogen chloride is a gas.

13. The method of claim 1 , wherein the hydrogen chloride is in excess.

14. The method of claim 9 , further comprising the step of dissolving the precipitate in water.

15. The method of claim 10 , further comprising the step of dissolving the precipitate in water.

16. The method of claim 11 , further comprising the step of dissolving the precipitate in water.