Chiral pyrrolidine core compounds en route to inhibitors of nitric oxide synthase
Diastereomeric pyrrolidine compounds and methods of preparation, as can be used en route to the preparation of a range of nitric oxide synthase inhibitors.
1. A method of preparing a chiral pyrrolidine compound, said method comprising:
providing a chiral dialkyl malate compound;
diastereoselective alkylation of said malate compound with a haloalkylpyridine compound, to provide an alkylated malate compound;
reduction of said alkylated malate compound, said reduction providing ester and aldehyde groups on said alkylated malate compound;
reductive amination of said aldehyde group of said alkylated malate compound, wherein said reductive amination provides an amine group, and reduction of said ester group of said alkylated malate compound, wherein said ester reduction provides an alcohol group; and
intramolecular cyclization of said alkylated malate compound with said amine group, to provide a chiral pyrrolidine compound.
2. The method of claim 1 wherein said chiral dialkyl malate compound is selected from (R)-(+)-malate and (S)-(−)-malate compounds.
3. The method of claim 2 wherein said chiral dialkyl malate compound has diisopropyl ester.
4. The method of claim 1 where said haloalkylpyridine compound is a bromomethylpyridine compound.
5. The method of claim 4 wherein said bromomethylpyridine compound is substituted with a protected amino group.
6. The method of claim 1 wherein said reductive amination is with a benzylamine.
7. The method of claim 1 wherein said alcohol group is mesylated.
8. The method of claim 1 wherein said reductive amination and said ester reduction are without ester-amine intermediate isolation.
9. The method of claim 1 comprising allylation of said alkylated malate compound.
10. The method of claim 9 wherein said allylation comprises treatment of said alkylated malate compound with hexamethyldisilazide.
11. A method of preparing a chiral pyrrolidine compound, said method comprising:
alkylation of a chiral dialkyl malate compound with a haloalkylpyridine compound to provide an alkylated malate compound;
allylation of said alkylated malate compound to provide an allylated and alkylated malate compound;
reduction of said allylated and alkylated malate compound, said reduction providing ester and aldehyde groups on said allylated and alkylated malate compound;
reductive amination of said aldehyde group of said allylated and alkylated malate compound, wherein said reductive amination provides an amine group, and reduction of said ester group of said allylated and alkylated malate compound, wherein said ester reduction provides an alcohol group; and
mesylation of said alcohol group of said allylated and alkylated malate compound under reaction conditions to promote intramolecular cyclization of said allylated and alkylated malate compound with said amine group, to provide a diastereomeric pyrrolidine compound.
12. The method of claim 11 wherein said chiral dialkyl malate compound is selected from (R)-(+)-malate and (S)-(−)-malate compounds.
13. The method of claim 12 wherein said chiral dialkyl malate compound has diisopropyl ester.
14. The method of claim 11 where said haloalkylpyridine compound is a bromomethylpyridine compound.
15. The method of claim 14 wherein said bromomethylpyridine compound is substituted with a protected amino group.
16. The method of claim 11 wherein said reductive amination is with a benzylamine.
17. The method of claim 11 wherein said reductive amination and said ester reduction are without ester-amine intermediate isolation.
18. The method of claim 11 comprising oxidation of the allyl moiety of said diastereomeric pyrrolidine compound to provide an aldehyde group, and reductive amination of said aldehyde group with an ethanamine.
19. A method of preparing a diastereomeric pyrrolidine compound, said method comprising:
providing an alkylated malate compound, said alkylated malate compound the diasteroselective alkylation product of a chiral dialkyl malate compound and a bromomethylpyridine compound;
reduction of said alkylated malate compound, said reduction providing ester and aldehyde groups on said alkylated malate compound;
reductive amination of said aldehyde group of said alkylated malate compound, wherein said reductive amination provides an amine group, and reduction of said ester group of said alkylated malate compound, wherein said ester reduction provides an alcohol group; and
mesylation of said alcohol group on said alkylated malate compound to promote intramolecular cyclization of said alkylated malate compound with said amine group, said cyclization providing one of a (3R,4R)- and a (3S,4S)-diastereomeric pyrrolidine compound.
20. The method of claim 19 wherein said chiral dialkyl malate compound is selected from (R)-(+)-malate and (S)-(−)-malate compounds.
21. The method of claim 20 wherein said chiral dialkyl malate compound has diisopropyl ester.
22. The method of claim 19 wherein said reductive amination is with a benzylamine.
23. The method of claim 19 comprising allylation of said alkylated malate compound.
24. The method of claim 23 comprising oxidation of the allyl moiety of said diastereomeric pyrrolidine compound to provide an aldehyde group, and reductive amination of said aldehyde group with a 2-phenylethanamine.