Functionalised carbocycles from carbohydrates. Part 5. The synthesis of the epoxybicyclo[3.2.0]heptanone ethylene acetal prostaglandin intermediate

Abstract

Treatment of the ethylene dithioacetal (4) of the bicyclo[3.2.0]heptanone derivative (3) with base gave specifically the hydroxy epoxide (8) which, with most nucleophiles, reacted at C-2 to give analogues of the starting material (4). The iodo dibenzoate (9) was then converted into the iodo lactone (11) from which the prostaglandin intermediate (6) has already been made. The corresponding ethylene acetal (5) was converted into the analogous epoxide (13) and thence into the diol (17) and the epoxybicyclo[3.2.0]heptanone ketal (7) which is a preferred, optically pure intermediate for prostaglandin synthesis.