(+)-(S)-S-3-(tert-butyldimethylsilyloxy)-2-oxobutyl O-ethyl carbonodithioate

S-(S)-1-[(3S,9S,14aR)-9-benzyl-6,6-dimethyl-1,4,7,10-tetraoxotetradecahydropyrrolo[1,2-a][1,4,7,10]tetraazacyclododecin-3-yl]-7-(tert-butyldimethylsilyloxy)-6-oxooctan-3-yl O-ethyl carbonodithioate

(-)-(3S,9S,14aR)-9-benzyl-3-[(S)-7-(tert-butyldimethylsilyloxy)-6-oxooctyl]-6,6-dimethyldecahydropyrrolo[1,2-a][1,4,7,10]tetraazacyclododecine-1,4,7,10-tetraone