Processes for making hydrazides
A method is disclosed for preparing hydrazides from hydrazine and an acyl chloride which comprises the steps of (a) preparing a stirred substantially uniform slurry comprising hydrazine and an inert solvent at low temperature; and (b) adding an acyl chloride continuously to said slurry. The method avoids or limits production of undesired bis-hydrazide by-products. The method is used to prepare 3-methyl-3-mercaptobutanoic acid hydrazide, a molecule used to link calicheamicin to a monoclonal antibody.
1. A method of preparing a hydrazide from hydrazine and an acyl halide comprising the steps of:
(a) preparing a slurry comprising hydrazine and an inert solvent; and
(b) adding an acyl halide continuously to said slurry, wherein the acyl halide further comprises a protected thiol.
2. The method according to claim 1 wherein the acyl halide is added substantially drop wise to the slurry.
3. The method according to claim 1 wherein the acyl halide comprises a benzyl thioether.
4. The method according to claim 1 wherein the acyl halide has the structure:
wherein P is a thiol protecting group;
R 1 and R 2 are each selected from the group consisting of C 1 -C 5 alkyl;
X is a halide; and
L is an alkylene linker.
5. The method according to claim 4 wherein L is —CH 2 —.
6. The method according to claim 4 wherein R 1 and R 2 are each independently methyl.
7. The method according to claim 4 wherein P is a benzyl group, optionally substituted on the phenyl ring.
8. The method according to claim 7 wherein P is p-methoxybenzyl group.
9. The method according to claim 1 wherein the acyl halide has the structure:
wherein X is a halide.
10. The method according to claim 1 wherein the inert solvent is methylene chloride.
11. The method according to claim 1 wherein said hydrazide product has the structure:
wherein P is a thiol protecting group;
R 1 and R 2 are each selected from the group consisting of C 1 -C 5 alkyl; and
L is an alkylene linker.
12. The method according to claim 11 wherein L is —CH 2 —.
13. The method according to claim 11 wherein R 1 and R 2 are each independently methyl.
14. The method according to claim 11 wherein P is a benzyl group, optionally substituted on the phenyl ring.
15. The method according to claim 14 wherein P is p-methoxybenzyl group.
16. The method according to claim 11 wherein the hydrazide product is
or a salt thereof.
17. The method according to claim 1 wherein the hydrazide contains less than 5% of a bis-hydrazide by-product having the structure:
wherein R and R′ are optionally substituted alkyl, heteroalkyl, or heteroalkaryl groups.
18. The method according to claim 17 wherein R and R′ are
wherein P is a thiol protecting group;
R 1 and R 2 are each selected from the group consisting of C 1 -C 5 alkyl; and
L is an alkylene linker.
19. The method according to claim 18 wherein L is —CH 2 —.
20. The method according to claim 19 wherein R 1 and R 2 are each independently methyl.
21. The method according to claim 18 wherein P is a benzyl group, optionally substituted on the phenyl ring.
22. The method according to claim 21 wherein P is p-methoxybenzyl group.
23. The method according to claim 22 wherein the bis-hydrazide by-product has the structure:
24. The method according to claim 1 wherein the continuous addition of acid halide solution is adjusted to maintain reaction temperature of about −68° C. to about −75° C.
25. A method of preparing 3-methyl-3-mercaptobutanoic acid hydrazide comprising the step of preparing a hydrazide according to the method of claim 15 .
26. A method of preparing an immunoconjugate of a member of the family of calicheamicins with a monoclonal antibody as carrier, which comprises preparing 3-methyl-3-mercaptobutanoic acid hydrazide according to the method of claim 25 and using the 3-methyl-3-mercaptobutanoic acid hydrazide for preparing said immunoconjugate.
27. The method according to claim 26 wherein 3-methyl-3-mercaptobutanoic acid hydrazide is used as a linker to make gemtuzumab ozogamicin or inotuzumab ozogamicin.
28. A method of preparing gemtuzumab ozogamicin comprising the steps of preparing the linker 3-methyl-3-mercaptobutanoic acid hydrazide according to the method of claim 25 and using said linker to link calicheamicin to the monoclonal antibody gemtuzumab.