Highly effective resolution of 1,3-dibenzyl-6-hydroxy-3,3a,6,6a-tetrahydro-1H-furo(3,4-d)imidazole-2,4-dione, an intermediate for biotin, with optically active amines and reutilization of the unwanted epimer.

The direct resolution of (3aRS, 6SR, 6aSR)-1, 3-dibenzyl-6-hydroxy-3, 3a, 6, 6a-tetrahydro-1H-furo[3, 4-d]imidazole-2, 4-dione [(±)-9], a key intermediate for biotin, with optically active amines was examined. Reaction of (±)-9 with cinchonidine readili gave the cinchonidine salt of the (4S, 5R)-aldehyde-carboxylic acid (12), acidification of which gave (3aS.6R, 6aR)-9, convertible to biothin. N-alkyl-D-glucamines (14) were also found to be effective resolving agents for (±)-9 applicable for industrial use. Reutilizatin of the unwanted epimer [(3aR, 6S, 6aS)-9] was effected by facile oxidation to the meso-diacid (3) with sodium chlorite.