Felbamate with improved bulk density
A synthesis and purification of felbamate, an anticonvulsant, are provided. The product of the synthesis and purification is with high untapped and tapped bulk densities, which increase ease of handling and suitability for use in pharmaceutical formulations. The felbamate may be incorporated into pharmaceutical compositions that can be administered orally for treatment of epilepsy.
1. A method of synthesizing felbamate, comprising the steps of:
(a) adding a solution of 2-phenyl-1,3-propanediol to a solution of chlorosulfonyl isocyanate while maintaining a temperature at less than about −20° C. over a first period ranging from about 10 minutes to about 60 minutes;
(b) maintaining temperature of the solution of 2-phenyl-1,3-propanediol and chlorosulfonyl isocyanate at less than about −20° C. for a second period ranging from about 30 minutes to about 45 minutes while stirring;
(c) adding water to the solution of 2-phenyl-1,3-propanediol and chlorosulfonyl isocyanate and increasing the temperature to a range of about 20° C. to about 40° C.;
(d) concentrating the solution of 2-phenyl-1,3-propanediol and chlorosulfonyl isocyanate after step (c);
(e) adding water to the solution of 2-phenyl-1,3-propanediol and chlorosulfonyl isocyanate after step (d) and cooling to about 5° C. to 30° C.; and
(f) isolating felbamate which precipitates from the solution of 2-phenyl-1,3-propanediol and chlorosulfonyl isocyanate.
2. The method of claim 1 where the solution of chlorosulfonyl isocyanate is cooled to about −20° C. to about −40° C. before the solution of 2-phenyl-1,3-propanediol is added in step (a).
3. The method of claim 1 where the solution of chlorosulfonyl isocyanate is cooled to about −30° C. to about −40° C. before the solution of 2-phenyl-1,3-propanediol is added in step (a).
4. A method for purifying felbamate prepared according to the method of claim 1 , comprising the steps of:
(a) dissolving the felbamate in a mixture comprising a solvent by heating the mixture to at least about 50° C. to form a solution;
(b) cooling the solution to a range of about 40° C. to about 50° C.;
(c) adding water to the solution from step (b) and cooling the solution to a range of about 0° C. to 10° C.; and
(d) isolating the felbamate which has formed crystals.
5. The method of claim 4 where the solvent is selected from the group consisting of ethanol, methanol, tetrahydrofuran, isopropanol, acetonitrile, water and mixtures thereof.
6. The method of claim 4 where the felbamate crystals have a tapped bulk density ranging from about 0.35 gm/ml to about 0.6 gm/ml.
7. The method of claim 6 where the tapped bulk density ranges from about 0.4 gm/ml to about 0.6 gm/ml.