RING CONTRACTION OF CYCLOBUTANES AND A NOVEL CASCADE REACTION - APPLICATION TO SYNTHESIS OF (+/-)-ANTHOPLALONE AND (+/-)-LEPIDOZENE

Two efficient and practical synthetic methodologies for the construction of small ring systems have been developed. The first method involves a novel rearrangement of cyclobutanes 10 and 14 leading to cyclopropanes 11 and 15 employing BF3.OEt(2) or POCl3 in the presence of pyridine or Raney nickel. The second method utilizes a novel cascade reaction of alpha,beta-unsaturated esters 25 and 36 possessing a cyclopropyl ketone moiety with TMSI in the presence of(TMS)(2)NH to afford polycyclic cyclobutane derivatives 26 and 38. A synthesis of(+/-)-anthoplalone (41) and a formal synthesis of (+/-)-lepidozene (42) were achieved utilizing 15, obtained by the above method.