The evaluation of 4-methylcamphor as an intermediate in Triterpenoid synthesis

A new synthetic route to (-)-4-methylcamphor 43 is described which involved initial conversion of (+)-camphor 1 to (-)-2-methylenebornane 41. Acid-catalyzed rearrangement of 41 provided ( +)-4-methylisobornyl acetate 40 which was reduced to (+)-4-methylisoborneol 42. Finally, oxidation of 42. produced (-)-4-methylcamphor 43. The optical purity of compounds 40 and 43 was determined by a chiral lanthanide shift reagent, [Eu[hfc)₃] 45 while the optical purity of 42 was determined by the Anderson-Shapiro reagent 48. Based on a mechanistic rationale, a different approach to the synthesis of optically pure 40 was attempted which involved the synthesis of a C(5)-substituted 2-methylenebornane derivative 58 from ( + ) -endo-3-bromocamphor 5a . The potential of (-)-4-methylcamphor 43 as a useful intermediate in the synthesis of triterpenoids belonging to the lanostane 49 structural sub-group was investigated. Through a series of bromination reactions followed by regioselective C-3 debromination, 43 was converted to 9,10-dibromo-4-(bromomethyl)camphor 75 which was cleaved to give 76, a possible precursor of a potentially useful intermediate 65 in triterpenoid synthesis.[See Thesis for Diagrams]Science, Faculty ofChemistry, Department ofGraduat