(2R,3S,4S)-4-Isopropenyl-3-methoxycarbonylmethyl-pyrrolidine-1,2-dicarboxylic acid 1-benzyl ester 2-ethyl ester

(2R,3S,4S)-3-Ethoxycarbonylmethyl-4-isopropenyl-pyrrolidine-1,2-dicarboxylic acid 1-benzyl ester 2-ethyl ester

1-(tert-butyl) 2-ethyl (2R,3S,4R)-4-(2-((tert-butyldimethylsilyl)oxy)propan-2-yl)-3-(2-ethoxy-2-oxoethyl)pyrrolidine-1,2-dicarboxylate

1-benzyl 2-ethyl (2R,3S,4R)-4-(2-((tert-butyldimethylsilyl)oxy)propan-2-yl)-3-(2-ethoxy-2-oxoethyl)pyrrolidine-1,2-dicarboxylate

(2R,3R,4R)-3-(Bis-ethoxycarbonyl-methyl)-4-[1-(tert-butyl-dimethyl-silanyloxy)-1-methyl-ethyl]-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-ethyl ester