FIELD: chemistry.
SUBSTANCE: invention relates to a method of splitting a racemic mixture of cis-2-hydroxymethyl-4-(cytosin-1'-yl)-1,3-oxathiolane to obtain an optically active mixture of cis-2-hydroxymethyl-4-(cytosin-1'-yl)-1,3-oxathiolane, involving the following steps: a) dissolving and heating said racemic mixture of cis-2-hydroxymethyl-4-(cytosin-1'-yl)-1,3-oxathiolane in a solvent in the presence of (1R)-(-)-10-camphorsulphonic acid and achiral acid to form a solution containing the following two diastereoisomeric salts: (-)-cis-2-hydroxymethyl-4-(cytosin-1'-yl)-1,3-oxathiolane• (1R)-(-)-10- camphorsulphonate and (+)-cis-2-hydroxymethyl-4-(cytosin-1'-yl)-1,3-oxathiolane•(1R)-(-)-10- camphorsulphonate; b) cooling the solution to facilitate crystallisation of diastereomeric salts; c) extraction of crystals of the optically active mixture of said two diastereomeric salts obtained at step b), which contains excess (-)-cis-2-hydroxymethyl-4-(cytosin-1'-yl)-1,3-oxathiolane• (1R)-(-)-10- camphorsulphonate over (+)-cis-2-hydroxymethyl-4-(cytosin-1'-yl)-1,3-oxathiolane•(1R)-(-)-10- camphorsulphonate, and d) treating said optically active mixture of said two diastereomeric salts to remove (1R)-(-)-10- camphorsulphonic acid in order to obtain an optically active mixture of cis-2-hydroxymethyl-4-(cytosin-1'-yl)-1,3-oxathiolane.
EFFECT: improved method.
16 cl, 3 tbl, 6 ex
