Synthesis of 3,5-dioxo-2-oxatricyclo [4.2.1.0^4.8]-nonane-(2,4-dioxo-5-oxabrendane)

Abstract

We report the synthesis of 3,5-dioxo-2-oxatricvclo[4.2.1.0^4.8[nonane (4) by a convenient and stereospecific procedure. The new compound 4 is related to brendane and may thus also be named 2,4-dioxo-5-oxabrendane (note different numbering!). Apart from the current interest in Brendane and its derivatives, the synthesis of 4 is noteworthy since this unknown compound has been a centre of dispute, previous attempted syntheses have failed, and its preparation now completes the set of the three synthetically and mechanistically useful systems: 4, the analogous 3,9-dioXll derivative ("4,9-dioxo-5-oxabrendane"), and the 3,7-dioxo derivative ("4,8-dioxo-5-oxabrendane"). In addition, the very detailed N.M.R. analysis of 4 has unequivocally clarified certain unusual features associated with assignments concerning the 3-oxo-2-oxa system (4-oxo-5-oxabrendane system). Finally, the synthetic utility of 4 has been demonstrated by the conversion of 4 into the dilactone 7 which is directly related to 12-norprostaglandins.