Methanesulfonic acid (1S,2R,3R)-2-benzyloxymethyl-3-(tert-butyl-dimethyl-silanyloxy)-1-[(S)-2-(tert-butyl-dimethyl-silanyloxy)-1-methyl-ethyl]-butyl ester

(2R,3R)-2-(tert-butoxycarbonylaminomethyl)-3-(tert-butyldimethylsiloxy)butyric acid