Patent ID: 8624033

Claim:
A process for the preparation of piperidineylsulfanylacetylmutilins of formula wherein the carbon atom of the piperidine ring attached to the sulphur atom is either in the (S)-configuration or in the (R)-configuration and the 2-amino-3-methyl-butyryl group attached to the piperidine ring is either in the (S)-configuration or in the (R)-configuration, comprising the steps of a) deprotecting a N-protected piperidineylsulfanylacetylmutilin of formula and isolating a crystalline compound of formula wherein the carbon atom of the piperidine ring attached to the sulphur atom is either in the (S)-configuration or in the (R)-configuration, in free form or in the form of an acid addition salt, in crystalline form, b) acylating said crystalline compound of formula III with either (R)- or (S)-valine protected as an enamine and activated as a carbonic acid mixed anhydride to form a compound of formula wherein R 1 and R 2 are C 1-4 alkyl, and R 3 is hydrogen or C 1-4 alkyl, and c) deprotecting the compound of formula IV and isolating the compound of formula I.