(1aS,2S,7aR)-2-(tert-butyldimethylsiloxy)-5-propyl-1a,7a-dihydro-2H-1,4-dioxa-cyclopropa[b]naphthalene-3,7-dione

(1aS,2S,7R,7aS)-2-(tert-butyldimethylsiloxy)-7-hydroxy-5-propyl-1a,2,7,7a-tetrahydro-3H-1,4-dioxa-cyclopropa[b]naphthalen-3-one

(1aS,2S,7S,7aS)-2-(tert-butyldimethylsiloxy)-7-hydroxy-5-propyl-1a,2,7,7a-tetrahydro-3H-1,4-dioxa-cyclopropa[b]naphthalen-3-one

(1S,2S,6R)-2-(tert-butyldimethylsiloxy)-5-oxo-4-[(E)-pent-1-enyl]-7-oxa-bicyclo[4.1.0]hept-3-ene-3-carboxylic acid

(1S,2S,6R)-2-(tert-butyldimethylsiloxy)-5-oxo-4-(1-pentenyl)-7-oxa-bicyclo[4.1.0]hept-3-ene-3-carboxylic acid 4-methoxybenzyl ester