(2R,3S)-methyl 3-(tert-butyldimethylsilyloxy)-2-((tert-butyl-dimethylsilyloxy)methyl)-5-oxopyrrolidine-2-carboxylate

(2R,3S)-methyl 3-(tert-butyldimethylsilyloxy)-2-((tert-butyldimethylsilyloxy)methyl)-1-(4-methoxybenzyl)-5-oxopyrrolidine-2-carboxylate

(2R,3S)-methyl 3-(tert-butyldimethylsilyloxy)-2-(hydroxy-methyl)-1-(4-methoxybenzyl)-5-oxopyrrolidine-2-carboxylate

(2S,3S)-methyl 3-(tert-butyldimethylsilyloxy)-2-formyl-1-(4-methoxybenzyl)-5-oxopyrrolidine-2-carboxylate

(3S)-methyl 3-(tert-butyldimethylsilyloxy)-2-((S)-1-hydroxy-2-methylallyl)-1-(4-methoxybenzyl)-5-oxopyrrolidine-2-carboxylate