(2S,5S)-2-benzyloxymethyl-8-(4-methoxybenzyl)-1-oxa-6,8-diazaspiro[4,4]nonane-3-ene-7,9-dione

5-E-<(2R,3R)-4-benzyloxy-2,3-isopropylidenedioxy>butylidene-3-(4-methoxybenzyl)hydantoin

(2'R,3'R,5Z)-5-(4'-benzyloxy-2',3'-isopropylidenedioxybutylidene)-3-(p-methoxybenzyl)hydantoin

(2R,5S)-2-benzyloxymethyl-8-(4-methoxybenzyl)-6-benzyloxycarbonyl-1-oxa-6,8-diazaspiro(4,4)nonane-3-ene-7,9-dione

(2R,3S,4R,5S)-2-benzyloxymethyl-8-(4-methoxybenzyl)-6-benzyloxycarbonyl-3,4-dihydroxy-1-oxa-6,8-diazaspiro[4,4]nonane-7,9-dione