Process for preparing R- and S-isomers of (R)-5-(2-( (2-(2-ethoxyphenoxy)ethyl)amino)propyl)-2-methoxybenzenesulfonamide

Abstract

A process for preparing optically pure enantiomers of R-(−)tamsulosin of formiula Ia and S-(+)tamsulosin of formula Ib by resolving racemic tamsulosin of formula I by means of (IR)-(−)-camphor-10-sulfonic acid and (1S)-(+)-camphor-10-sulfonic acid, resp., in an environment of organic solvents, water or mixtures thereof.

1. A process for preparing optically pure enantiomers of (R)-5-(2-((2-(2-ethoxyphenoxy)-ethyl)amino)propyl)-2-methoxybenzenesulfonamide [R-(−)-tamsulosin] of formula Ia 
                 
 
       and (S)-5-(2-((2-(2-ethoxyphenoxy)-ethyl)amino)propyl)-2-methoxybenzenesulfonamide [S-(+)-tamsulosin] of formula Ib 
                 
 
       comprising:
 (a) the resolution of racemic tamsulosin of formula I 
                 
 
 
       by the treatment with (1R)-(−)-camphor-10-sulfonic acid and (1S)-(+)-camphor-10-sulfonic acid, resp., in an environment of organic solvents, water or mixtures thereof;
 (b) further purification of the crystallized salt of R-(−)-tamsulosin or S-(+)-tamsulosin by crystallizing form organic solvents, water or mixtures thereof, until the desired optical purity is obtained;  
 (c) from the salt of R-(−)-tamsulosin or S-(+)-tamsulosin is released, by treatment with alkalis, the base of formula Ia or the base of formula Ib, resp.  
 
     
     
       2. The process of  claim 1  wherein steps (a) and (b) are carried out in an environment of alcohols. 
     
     
       3. The process of  claim 1  wherein steps (a) and (b) are carried out in an environment of water. 
     
     
       4. A process which comprises:
 (a) preferentially precipitating one diastereomeric camphor sulfonate salt of tamsulosin from a solution containing a pair of diastereomeric camphor sulfonate salts of tamsulosin to form diastereomeric enriched precipitate and diastereomeric enriched solute.  
 
     
     
       5. The process according to  claim 4 , which further comprises forming said solution by dissolving a solid mixture of a pair of diastereomeric camphor sulfonate salts of tamsulosin in a solvent.