Formation of tricyclo[6.3.0.02,5]undecane derivatives during attempts to make the rumphellatin A–C oxacarbon skeleton

Abstract

The results of several approaches to make the 4,4,8-trimethyl-12-oxatricyclo[7.2.1.02,5]dodecane motif present in rumphellatins A–C are reported. The strategy adopted involved (9E)-12,12-dimethyl-5-oxatricyclo[8.2.0.04,6]dodec-9-en-11-ol as an intermediate, but when attempts were made to connect the third methyl group to the carbon skeleton by reacting the epoxide with MeLi under boron-trifluoride catalysis, an unprecedented transannular reaction occurred. The desired product was not formed; instead, compounds containing a tricyclo[6.3.0.02,5]undecane moiety were obtained, in one case in better than 70% yield.