Claims for Patent: 6,294,572

Summary for Patent: 6,294,572

Title:	Crystalline N-acetyl neuraminic acid derivatives and process for their preparation
Abstract:	Two useful crystal hydrates of 5-acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galacto-non-2-enopy ranosonic acid have either a low or high aspect ratio. These crystalline N-acetyl neurominic acid derivatives are favored for pharmaceutical formulation because of their physical properties. For example, the low aspect ratio crystal has good flow properties, and the high aspect ratio crystal has a stable water content over time.
Inventor(s):	Williamson; Christopher (Stevenage, GB), White; William James (Stevenage, GB), Patel; Vipulkumar (Stevenage, GB)
Assignee:	Biota Scientific Management Pty Ltd. (Glen Iris, AU)
Application Number:	09/346,583
Patent Claims:	1. 5-Acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galacto-non-2-enopy ranoasonic acid in crystalline hydrate form, wherein the crystals have a low aspect ratio and an X-ray diffraction trace having the line intensities at the indicated d-spacings essentially as shown: or wherein the crystals have a high aspect ratio and an X-ray diffraction trace having the line intensities at the indicated d-spacings essentially as shown: 2. 5-Acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galacto-non-2-enopy ranosonic acid according to claim 1, in the form of crystals having a low aspect ratio. 3. The crystalline hydrate form as claimed in claim 2, wherein the hydrate crystals are tabular. 4. The crystalline hydrate form as claimed in claim 2, wherein substantially all water of crystallization is lost at about 80 to 90.degree. C. 5. 5-Acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galacto-non-2-enopy ramosonic acid according to claim 1, in the form of dihydrate crystals having a high aspect ratio. 6. The crystalline dihydrate form as claimed in claim 5, wherein the dihydrate crystals are needle-shaped. 7. The crystalline dihydrate form as claimed in claim 5, wherein water content is stable over a broad range of relative humidity. 8. The crystalline dihydrate form as claimed in claim 5, wherein one mole of water of crystallization is lost by about 135-143.degree. C. 9. The crystalline hydrate of claim 1, wherein the crystalline hydrate is substantially free of the crystalline hydrate form having a high aspect ratio. 10. The crystalline hydrate of claim 1, wherein the crystalline hydrate is substantially free of the crystalline hydrate form having a low aspect ratio. 11. 5-Acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galacto-non-2-enopy ramosonic acid as claimed in claim 1, in micronized form. 12. A pharmaceutical formulation comprising 5-acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galacto-non-2-enopy ramosonic acid in crystalline hydrate form, and a pharmaceutically acceptable carrier therefor, wherein the crystals have a low aspect ratio and an X-ray diffraction trace having the line intensities at the indicated d-spacings essentially as shown: or wherein the crystals have a high aspect ratio and an X-ray diffraction trace having the line intensities at the indicated d-spacings essentially as shown: 13. A pharmaceutical formulation as claimed in claim 12, in the form of a powder. 14. A pharmaceutical formulation comprising 5-acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galacto-non-2-enopy ranosonic acid as claimed in claim 1, in micronized form, and a pharmaceutically acceptable carrier therefor. 15. A method for the preparation of 5-acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galacto-non-2-enopy ranosonic acid in crystalline hydrate form, which method comprises crystallization of 5-acetamido-2,3,4,5-tetradeoy-4-guanidino-D-glycero-D-galacto-non-2-enopyr anosonic acid from aqueous solution, wherein the crystals have a low aspect ratio and an X-ray diffraction trace having the line intensities at the indicated d-spacing essentially as shown: or wherein the crystals have a high aspect ratio and an X-ray diffraction trace having the line intensities at the indicated d-spacings essentially as shown: 16. A method as claimed in claim 15, for the preparation of a crystalline hydrate of said compound having a low aspect ratio. 17. A method as claimed in claim 16, wherein the temperature of the aqueous solution is greater than about 50.degree. C. 18. A method as claimed in claim 17, wherein the temperature of the aqueous solution is in the range of 50 to 55.degree. C. 19. A method as claimed in claim 16, wherein the aqueous solution is seeded with crystals of the crystalline hydrate form having a low aspect ratio. 20. A method as claimed in claim 15, for the preparation of the crystalline dihydrate form having a high aspect ratio. 21. A method as claimed in claim 20, wherein the temperature of the aqueous solution is less than about 40.degree. C. 22. A method as claimed in claim 21, wherein the temperature of the aqueous solution is in the range 20 to 30.degree. C. 23. A method as claimed in claim 20, wherein the aqueous solution is seeded with crystals of the crystalline dihydrate form having a high aspect ratio. 24. A method as claimed in claim 15, comprising the step of addition of a counter solvent to the aqueous solution. 25. A method as claimed in claim 24, wherein the counter solvent is a ketone or an alkanol. 26. A method as claimed in claim 25, wherein the counter solvent is acetone. 27. A method for the preparation of the crystalline hydrate form as claimed in claim 2, which method comprises interconversion of the crystalline dihydrate form having a high aspect ratio. 28. The method as claimed in claim 27, wherein interconversion is effected by aging of the aqueous solution. 29. The method as claimed in claim 27, wherein the interconversion is effected by addition of a base to the aqueous solution. 30. A method for the preparation of the crystalline dihydrate form as claimed in claim 5, which process comprises addition of an aqueous solution of 5-acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galacto-non-2-enopy ranosonic acid to a similar volume of a counter solvent. 31. The method as claimed in claim 30, wherein the counter solvent is acetone. 32. A method for the preparation of the pharmaceutical formulation in the form of an aqueous solution or suspension, which method comprises dissolution in water of crystalline hydrate of 5-acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galacto-non-2-enopy ranosonic acid, wherein the crystals have a low aspect ratio and an X-ray diffraction trace having the line intensities at the indicated d-spacings essentially as shown: or wherein the crystals have a high aspect ratio and an X-ray diffraction trace having the line intensities at the indicated d-spacings essentially as shown: