Preparation and some reactions of 2-oxatricyclo[3.3.0.0]oct-7-en-3-one : synthesis of 9-deoxa-9,10-dehydroprostaglandin D2

Abstract

The tricyclic lactone (1) was prepared by two methods. Reaction of (1) with electrophilic reagents occurred on the more exposed exo-face of the alkene unit resulting in the formation of the epoxylactone (8) on peracid oxidation and the bromolactones (9)–(11) on bromination in the appropriate solvent. Thiophenoxide ion reacted with (1) in S_N2 fashion to give the acid (13) while deuteriation studies suggested that lithium dibutylcuprate reacted with (1) through the S_N′ pathway preferentially to give the acid (15). The cuprate reagent (20) reacted with the lactone (1) to form the acid (21) which was converted into the prostanoid (29) in a standard fashion.