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

(2R,3S)-2-Benzyloxymethyl-3-hydroxy-4-iodomethyl-1-(4-methoxy-benzyl)-3-methyl-5-oxo-pyrrolidine-2-carboxylic acid methyl ester

methyl (2R,3S)-1-(4-methoxybenzyl)-2-((benzyloxy)methyl)-3-hydroxy-3-methyl-4-methylene-5-oxopyrrolidine-2-carboxaldehyde

(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

(3R,3aS,7aR)-3-[(S)-1-(Isopropyl-dimethyl-silanyloxy)-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