(2aS,3S,7bS)-3-(tert-Butyl-dimethyl-silanyloxy)-4-eth-(Z)-ylidene-2a,3,4,6,7,7b-hexahydro-2-oxa-7a-aza-cyclopenta[cd]inden-1-one

(1S,8aS)-1-((S)-1-Hydroxy-but-2-ynyl)-8,8a-dihydro-1H-oxazolo[3,4-a]pyridine-3,7-dione

(1S,8aR)-8-Bromo-1-[(S)-1-(tert-butyl-dimethyl-silanyloxy)-but-2-ynyl]-1,5,6,8a-tetrahydro-oxazolo[3,4-a]pyridin-3-one

(1S,8R,8aR)-8-Bromo-1-[(S)-1-(tert-butyl-dimethyl-silanyloxy)-but-2-ynyl]-8,8a-dihydro-1H-oxazolo[3,4-a]pyridine-3,7-dione