Studies of the Haller-Bauer and homo-Nazarov reactions. Approaches to pentalenolactone P and a (3);peristylane derivative

The Haller-Bauer cleavage of optically active 3-benzoyl-3-phenyl-1-isopropylidenecyclopentane (11), its silyl analogue 23, and cis- and trans-1-benzoyl-1-phenyl-4-tert-butylcyclohexanes (41 and 50) have been studied. The fragmentations of 11 and 23 proceed with high retention of configuration in non-dissociating solvents. The latter example showed higher degrees of retention under otherwise similar conditions, probably due to the ;A new synthetic path that leads to a specifically functionalized (3) peristylane is described. This method features construction of a cyclopropane ring at an earlier stage via the oxa-di-;Synthetic efforts toward the total synthesis of pentalenolactone P are also described. This study shows that the stage at which the cyclopropane ring is introduced seemingly controls the entire synthetic scheme. Several approaches to the fused cyclopropane structure in pentalenolactone P have been studied. The stereospecific attachment of the cyclopropane ring to the diquinane nucleus at an early stage was ultimately pursued. The Diels-Alder reaction of 1-methylcycloheptatriene with fumaric acid derivatives and ensuing selective lactonization were implemented to serve this end.;A general approach for regiocontrolled joining of a 2-cyclohexenone to an existing carbonyl functionality is outlined. The requisite conditions are sufficiently mild to be useful in a wide variety of applications.