(3R,3aS,7aR)-3-((S)-1-Hydroxy-2-methyl-propyl)-2-(4-methoxy-benzyl)-3a,5,5-trimethyl-1-oxo-octahydro-4-oxa-2-aza-5-sila-indene-3-carboxylic acid methyl ester

(2R,3S,4R)-3-Hydroxy-4-(2-hydroxy-ethyl)-2-[(S)-1-(isopropyl-dimethyl-silanyloxy)-2-methyl-propyl]-3-methyl-5-oxo-pyrrolidine-2-carboxylic acid methyl ester

(2R,3S,4R)-3-Hydroxy-2-((S)-1-hydroxy-2-methyl-propyl)-3,4-dimethyl-5-oxo-pyrrolidine-2-carboxylic acid methyl ester

(2R,3S,4R)-2-Hydroxymethyl-1-(4-methoxy-benzyl)-3,4-dimethyl-5-oxo-3-triethylsilanyloxy-pyrrolidine-2-carboxylic acid methyl ester

(2R,3S,4R)-2-((S)-1-Hydroxy-2-methyl-propyl)-1-(4-methoxy-benzyl)-3,4-dimethyl-5-oxo-3-triethylsilanyloxy-pyrrolidine-2-carboxylic acid methyl ester