L-malate salts of (6-(5-chloro-2-pyridyl)-5-[(4-methyl-1-piperazinyl) carbonyloxy]-7-oxo-67-dihydro-5H-pyrrolo[34-b]pyrazine) are provided.

Besylate salts of (6-(5-chloro-2-pyridyl)-5-[(4-methyl-1-piperazinyl)carbonyloxy]-7-oxo-67-dihydro-5H-pyrrolo[34-b]pyrazine) are provided.

The present invention provides a process for the preparation of the dextrorotatory isomer of zopiclone (eszopiclone). The present invention also provides eszopiclone di-p-anisolyl-L-tartrate and eszopiclone diacetyl-L-tartrate which are useful as intermediates in a process for preparing eszopiclone.

Present invention relates to an improved process for the preparation of Zopiclone and its enantiomerically enriched isomer (Eszopiclone). 6-(5-Chloropyridin-2-yl)-5-hydroxy-7-oxo-56-dihydropyrrolo[34-b]pyrazine is reacted with 1-chloro-carbonyl-4-methylpiperazine in the presence of alkali earth metal carbonates hydroxides or oxides in a solvent medium to give Zopiclone. It is reacted with optically active acid in a mixture of water and water miscible organic solvent followed by work up to give E...