Lysine-based prodrugs of aspartyl protease inhibitors and processes for their preparation

1. A process for synthesizing a compound of formula IIIA:

the process comprising the step of acylating a compound of formula XIV:

with a reactive amino acid having structure:

wherein LG represents a leaving group and

wherein n is 3 or 4,

wherein X and Y, the same or different, are selected from the group consisting of H, a straight alkyl group of 1 to 6 carbon atoms, a branched alkyl group of 3 to 6 carbon atoms, a cycloalkyl group of 3 to 6 carbon atoms, F, Cl, Br, I, —CF 3 , —OCF 3 , —CN, —NO 2 , —NR 4 R 5 , —NHCOR 4 , —OR 4 , —SR 4 , —COOR 4 , —COR 4 , and —CH 2 OH or X and Y together define an alkylenedioxy group selected from the group consisting of a methylenedioxy group of formula —OCH 2 O— and an ethylenedioxy group of formula —OCH 2 CH 2 O—,

wherein R 3 is selected from the group consisting of H, a straight alkyl group of 1 to 6 carbon atoms, a branched alkyl group of 3 to 6 carbon atoms, a cycloalkyl group of 3 to 6 carbon atoms, and a group of formula R 3A —CO—, wherein R 3A is selected from the group consisting of a straight or branched alkyl group of 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, a cycloalkylalkyl group having 3 to 6 carbon atoms in the cycloalkyl part thereof and 1 to 3 carbon atoms in the alkyl part thereof, an alkyloxy group of 1 to 6 carbon atoms, tetrahydro-3-furanyloxy, —CH 2 OH, —CF 3 , —CH 2 CF 3 , —CH 2 CH 2 CF 3 , pyrrolidinyl, piperidinyl, 4-morpholinyl, CH 3 O 2 C—, CH 3 O 2 CCH 2 —, Acetyl-OCH 2 CH 2 —, HO 2 CCH 2 —, 3-hydroxyphenyl, 4-hydroxyphenyl, 4-CH 3 OC 6 H 4 CH 2 —, CH 3 NH—, (CH 3 ) 2 N—, (CH 3 CH 2 ) 2 N—, (CH 3 CH 2 CH 2 ) 2 N—, HOCH 2 CH 2 NH—, CH 3 OCH 2 O—, CH 3 OCH 2 CH 2 O—, C 6 H 5 CH 2 O—, 2-pyrrolyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-pyrazinyl, 2-quinolyl, 3-quinolyl, 4-quinolyl, 1-isoquinolyl, 3-isoquinolyl, 2-quinoxalinyl, a phenyl group of formula:

a picolyl group selected from the group consisting of

a picolyloxy group selected from the group consisting of

a substituted pyridyl group selected from the group consisting of

and a group of formula:

wherein R 2 is selected from the group consisting of a diphenylmethyl group of formula IV:

a naphthyl-1-CH 2 — group of formula V:

a naphthyl-2-CH 2 — group of formula VI:

wherein X′ and Y′, the same or different, are selected from the group consisting of H, a straight alkyl group of 1 to 6 carbon atoms, a branched alkyl group of 3 to 6 carbon atoms, a cycloalkyl group of 3 to 6 carbon atoms, F, Cl, Br, I, —CF 3 , —NO 2 , —NR 4 R 5 , —NHCOR 4 , —OR 4 , —SR 4 , —COOR 4 , —COR 4 and —CH 2 OH,

wherein R 4 and R 5 , the same or different, are selected from the group consisting of H, a straight alkyl group of 1 to 6 carbon atoms, a branched alkyl group of 3 to 6 carbon atoms, a cycloalkyl group of 3 to 6 carbon atoms, and tert-butoxycarbonyl, and

wherein R 6 is selected from the group consisting of a straight alkyl group of 1 to 6 carbon atoms, a branched alkyl group of 3 to 6 carbon atoms, a cycloalkylalkyl group having 3 to 6 carbon atoms in the cycloalkyl part thereof and 1 to 3 carbon atoms in the alkyl part thereof.

2. The process of claim 1 , wherein the acylating step comprises:

a. increasing the alkalinity of an aqueous solution comprising the compound of formula XIV up to pH 7 to pH 10,

b. adding a solution comprising the reactive amino acid in a dipolar aprotic solvent and allowing reaction between the compound of formula XIV and the reactive amino acid by agitation for a period of about 1 to about 24 hours at a temperature of about 0° C. to about 40° C., and

c. extracting the compound of formula IIIA from an aqueous phase comprising a compound of formula IIIA with a suitable solvent.

3. The process of claim 2 , wherein the aqueous phase is acidified before being extracted with the solvent.

4. The process of claim 2 , wherein said suitable solvent is evaporated.

5. The process of claim 3 , further comprising recovering compound of formula III:

wherein R 2 and R 3 are as defined in claim 1 .

6. The process of claim 1 , wherein n is 4.

7. The process of claim 4 , wherein X and Y, the same or different, are selected from the group consisting of methyl, ethyl, H, F, Cl, Br, I and —NR 4 R 5 .

8. The process of claim 7 , wherein X and Y, the same or different, are selected from the group consisting of H, F and NH 2 .

9. The process of claim 8 , wherein X is NH 2 and Y is H or F.

10. The process of claim 9 , wherein X is 4-NH 2 .

11. The process of claim 9 , wherein Y is 3-F.

12. The process of claim 1 , wherein R 6 is selected from the group consisting of a straight alkyl group of 1 to 6 carbon atoms and a branched alkyl group of 3 to 6 carbon atoms.

13. The process of claim 12 , wherein R 6 is iso-butyl.

14. The process of claim 1 , wherein the reactive amino acid has structure:

wherein R 2 and R 3 are as defined in claim 1 .

15. A process for synthesizing a compound of formula IIIB:

the process comprise the step of acylating a compound of formula XIX:

with a reactive amino acid of formula:

16. The process of claim 15 , wherein the acylating step comprises:

a. increasing the alkalinity of an aqueous solution comprising the compound of formula XIV up to pH 7 to pH 10,

b. adding a solution comprising the reactive amino acid in a dipolar aprotic solvent and allowing reaction between the PL-461 compound and the reactive amino acid by agitation for a period of about 1 to about 24 hours, and

c. extracting the compound of formula IIIB from an aqueous phase comprising the IIIB compound with a suitable solvent.

17. The process of claim 16 , wherein the aqueous phase is acidified before being extracted with said suitable solvent.

18. The process of claim 16 , wherein the solvent is evaporated.

19. A process for the preparation of compound IIIB:

said process comprising the steps of

a) phosphorylating a compound of formula XVII:

 in the presence of an organic base in a dipolar aprotic solvent,

b) hydrolysizing the compound obtained in a) in the presence of concentrated hydrochloric acid to provide a water soluble hydrochloric salt of phosphoric acid mono ester, and

c) acylating an aqueous solution of b) with a suitable reactive amino acid of the formula:

to provide the phosphate mono ester of formula IIIB:

20. The process of claim 19 , wherein the dipolar aprotic solvent is methyl iso-butyl ketone or acetone.

21. The process of claim 20 , wherein said suitable reactive amino acid is a compound of formula: