Process and intermediates for the preparation of (1R,2S,5S)-6,6-dimethyl-3-azabicyclo[3,1,0]hexane-2-carboxylates or salts thereof
View Patent ↗In one embodiment, the present application relates to a process of making a compound of formula I. and to certain intermediate compounds that are made within the process of making the compound of formula I.
1. A process of making a compound of formula I:
or salts thereof, said process comprising:
(1) desymmetrizing a compound of formula II with R 1 OH in the presence of a chiral reagent to yield a compound of formula III:
wherein R 1 is selected from the group consisting of alkyl, trifluoroethyl, trichloroethyl, alkenyl, aryl, aralkyl, alkylaryl, cycloalkyl, cycloalkylalkyl, cycloalkenyl and cycloalkenylalkyl;
(2) aminating the compound of formula III to yield a compound of formula IV:
(3) reducing the amide and ester functionalities of the compound of formula IV to yield a compound of formula V:
(4) protecting the amino group of the compound of formula V to yield a compound of formula VI:
wherein P represents a protecting group;
(5) oxidizing the compound of formula VI to yield a compound of formula VII:
(6) adding R 2 OH to the compound of formula VII to yield a compound of formula VIII:
wherein R 2 represents H, alkyl, aryl, aralkyl, cycloalkyl or cycloalkylalkyl;
(7) cyanating the compound of formula VIII to yield a compound of formula IX:
(8) hydrolyzing the compound of formula IX with MOR 3 or R 3 OH into a compound of formula X:
wherein M is selected from the group consisting of Li, Na and K, and R 3 is selected from the group consisting of alkyl, aryl, aralkyl and cycloalkyl; and
(9) deprotecting the compound of formula X to yield the compound of formula I:
or optionally isolating it as salts thereof.
2. The process according to claim 1 , wherein R 1 is selected from the group consisting of methyl, ethyl, trifluoroethyl, trichloroethyl, propyl, isopropyl, allyl, 3-methyl-2-butenyl and cinnamyl.
3. The process according to claim 1 , wherein R 1 is allyl.
4. The process according to claim 1 , wherein P represents a Cbz protecting group from a reagent selected form the group consisting of Cbz-Cl, 2-chloro-Cbz-Cl, 2,4-dichloro-Cbz-Cl and 4-bromo-Cbz-ClCbz-Cl.
5. The process according to claim 1 , wherein R 2 represents (C 1 -C 6 )alkyl.
6. The process according to claim 1 , wherein R 3 represents (C 1 -C 6 )alkyl.
7. The process according to claim 1 , wherein said chiral reagent is selected from the group consisting of cinchona alkaloids, enzymes, and diisopropoxytitanium TADDOL-ates.
8. The process according to claim 7 , wherein said cinchona alkaloid is selected from the group consisting of quinidine, modified quinidine, cinchonine, epicinchonidine and epiquinine.
9. The process according to claim 8 , wherein said cinchona alkaloid is quinidine.
10. The process according to claim 1 further comprising making a salt of the compound of formula III by adding a primary, secondary or tertiary amine.
11. The process according to claim 10 , wherein said primary amine is R(+)-α-methylbenzylamine.
12. The process according to claim 1 , wherein step 2 comprises adding a source of ammonium, a source of carboxylic acid activation, and a base to the reaction.
13. The process according to claim 12 , wherein said ammonium source is selected from the group consisting of ammonium hydroxide, ammonium chloride, ammonium bicarbonate, and ammonium phosphate.
14. The process according to claim 12 , wherein said source of carboxylic activation is selected from the group consisting of di-tert-butyl-dicarbonate and isobutyl chloroformate.
15. The process according to claim 12 , wherein said base is pyridine.
16. The process according to claim 1 , wherein the reduction in step 3 comprises a first stage and a second stage, wherein said first stage comprises reducing the ester of the compound of formula V with a reducing agent selected from the group consisting of alane, lithium borohydride, and sodium borohydride in the presence of trimethylsilyl, and said second stage comprises reducing the amide of the compound of formula V to an amine with a reducing agent selected from the group consisting of lithium aluminum hydride and sodium triacetoxyborohydride.
17. The process according to claim 1 , wherein the compound of formula V in step 3 is isolated as a salt selected from the group consisting of a benzoate salt, a camphoric salt, a dibenzoyl tartaric acid salt, a fumaric acid salt, and a 4-chlorobenzoic acid salt.
18. The process according to claim 17 , wherein the compound of formula V in step 3 is isolated as a salt having the following structure:
19. The process according to claim 1 , wherein the oxidation of the compound of formula VI in step 5 is carried out using TEMPO mediated oxidation.
20. The process according to claim 1 , wherein step 6 further comprises adding an acid selected from the group consisting of inorganic acid, organic acid, and Lewis acid.
21. The process according to claim 1 , wherein the compound of formula VIII in step 7 is treated with trimethylsilyl cyanide or potassium cyanide.
22. The process according to claim 1 , wherein step 7 further comprises adding a catalyst selected from the group consisting of boron triluoride etherate, trifluoromethane sulfonic acid, trimethylsilyl ester and SnCl 4 .
23. The process according to claim 1 , wherein the compound of formula X is deprotected in a suitable solvent in the presence of Pd—C under 30-180 psi of hydrogen to yield the compound of formula I.
24. The process according to claim 1 , wherein the compound of formula I in step 9 is isolated as a salt selected from the group consisting of an HCl salt, a p-toluene sulfonic acid salt, a 4-chlorobenzene sulfonic acid salt, and a hydrogen bromide salt.
25. The process according to claim 24 , wherein the compound of formula I in step 9 is isolated as a salt of the following structure: