| abstract |
The present invention is directed at a process for selectively removing compound of formula 1 or a salt thereof from a mixture comprising compound of formula I and compound of formula 4: see formula 4 wherein the process comprises the steps of: (i) putting the mixture in solution and treating the solution with a reactant selected from the group consisting of: see formula (A) where X is halogen, OH or OCOR'; Hal is halogen; Y is O or S; W is O, N or S; and R, R', and R" are each independently selected from the group consisting of alkyl, aryl, and aralkyl; to yield protected compounds of formula 5 and diprotected compounds of formula 6, see formula 6 said protected compounds of formula 5 and diprotected compounds of formula 6 being soluble in the solution; (ii) hydrolysis, in a suitable solvent, of the protected compounds of formula 5 and the diprotected compounds of formula 6 by using a metal hydroxide or metal carbonate, to yield soluble compounds of formula 1 and soluble protected compounds of formula 7; see formula 7 (iii) adding an acid, preferably sulfuric acid, to form an insoluble salt of compounds of formula 1; (iv) isolating the insoluble salt of compound of formula 1; and optionally, recovering the compound of formula 1 from its salt. |