The present invention relates to a process for producing compounds of formula (I) and (VII); said process comprising the steps of: a) subjecting a compound of formula (II) to an enzymatic diastereomeric resolution in the presence of a suitable amount of enzyme chosen from Pig Liver Esterase or Porcine Pancreatic Lipase b) recovering said compounds of formula (I) and (VII). The invention also provides a process for producing compounds of formula (III) and (X); said process comprising the steps of: a) subjecting a compound of formula (IV) to an enzymatic diastereomeric resolution in the presence of a suitable amount of enzyme chosen from Candida Antarctica “A” lipase, Candida Antarctica “B” lipase, Candida Lypolitica Lipase or Rhizomucor Miehei Lipase b) recovering said compound of formula (III) and (X).