Preparation of d-2-amino-1-butanol salts

Abstract

A racemic mixture of dl-2-amino-1-butanol is resolved with separation of the d-2-amino-1-butanol by crystallizing as a salt with L(+)-tartaric acid from an essentially anhydrous solution in ethanol or methanol. The salt is decomposed with calcium hydroxide to yield the d-2-amino-1-butanol. Water may be added to the residual anhydrous solution to separate the l-2-amino-1-butanol. Other listed volatile solvents may be present in the anhydrous ethanol or methanol without inhibiting the sharp separation.

We claim: 
     
       1. The process of preparing the acid L-tartrate of d-2-amino-1-butanol comprising forming a solution of dl-2-amino-1-butanol in a solvent consisting essentially of an anhydrous lower alkanol selected from the group consisting of methanol and ethanol and not more than 1.0% water, adding thereto L-tartaric acid in at least about a one-half molar quantity, and separating the crystalline acid L-tartrate of d-2-amino-1-butanol. 
     
     
       2. The process of claim 1 in which the solvent is essentially anhydrous methanol. 
     
     
       3. The process of claim 1 in which the solvent is essentially anhydrous ethanol. 
     
     
       4. The process of claim 1 in which the solvent is essentially an anhydrous mixture of ethanol and methanol. 
     
     
       5. A process for separating d-2-amino-1-butanol from dl-2-amino-1-butanol comprising following the process of claim 1, then suspending the acid L-tartrate salt of d-2-amino-1-butanol in a water-containing solvent, adding an alkaline earth oxide or hydroxide, separating the alkaline earth L-tartrate and fractionally distilling the remaining layer to obtain d-2-amino-1-butanol. 
     
     
       6. The process of claim 5 in which the separation of the tartrate salt is conducted in water. 
     
     
       7. The process of claim 6 in which about a stoichiometric quantity of sulfuric acid and sufficient water to dissolve the L-tartaric acid is added to the alkaline earth L-tartrate, the calcium sulfate formed is separated out and free L-tartaric acid is recovered by evaporating off the water. .Iadd. 8. In the preparation of the (+)2,2'-(ethylenediimino) di-1-butanol dihydrochloride, the improvement comprising the process of preparing the acid L-tartrate of d-2-amino-1-butanol comprising forming a solution of dl-2-amino-1-butanol in a solvent consisting essentially of an anhydrous lower alkanol selected from the group consisting of methanol and ethanol and not more than 1.0% water, adding thereto L-tartaric acid in at least about a one-half molar quantity, and separating the crystalline acid L-tartrate of d-2-amino-1-butanol. .Iaddend. .Iadd. 9. In the process of preparing d-2-amino-1-butanol from dl-2-amino-1-butanol, the step which comprises separating d-2-amino-1-butanol (+) hydrogen tartrate from l-2-amino-1-butanol (+) hydrogen tartrate by fractional crystallization in anhydrous methyl alcohol in which the d-2-amino-1-butanol (+) hydrogen tartrate is comparatively insoluble and the anhydrous l-2-amino-1-butanol (+) hydrogen tartrate is very soluble. .Iaddend.