p. 3491 - 3494
(2001)p. 17250 - 17251
(2009/07/19)p. 587 - 590
(2007/10/03)(2R,5S,6S,8S)-1-Benzoyl-8-isobutyl-4-oxo-2,6-diphenyl-3-oxa-1,7-diaza-spiro[4.4]nonane-8-carboxylic acid methyl ester
(2S,4S,5S)-4-Benzoylamino-2-isobutyl-5-phenyl-pyrrolidine-2,4-dicarboxylic acid dimethyl ester
(2S,5R,6R,8R)-1-Benzoyl-2-tert-butyl-8-isobutyl-4-oxo-6-phenyl-3-oxa-1,7-diaza-spiro[4.4]nonane-8-carboxylic acid methyl ester