A PROCESS FOR THE PREPARATION OF 14-O-[(N-(3-METHYL-2-AMINO-BUTYRYL-PIPERIDINYL)SULFANYL ACETYL]MUTILINS OF FORMULA FEASIBLE FOR LARGE-SCALE PRODUCTION OF HIGH PURITY PRODUCTS, AND WHEREIN THE CARBON ATOM AT THE PIPERIDINE RING ATTACHED TO THE SULPHUR ATOM IS EITHER IN THE (S)- CONFIGURATION OR IN THE (R)-CONFIGURATION, AND A NEW CRYSTALLINE FORM OF 14-O-[(N-3-METHYL-2-(R)-AMINO-BUTYRYL-PIPERIDINE-3(S)-YL)SULFANYL)ACETYL]MUTILIN - HYDROCHLORIDE.