| The 7,8-epoxy-2-basmen-6-one ring system can be assembled efficiently by the Claisen ring expansion strategy reported here. This methodology would appear to hold considerable synthetic utility, different aspects of which are currently being explored in other contexts. Its particular value resides in the conciseness and efficiency with which eight-membered ring construction can be achieved from structurally simpler lactone precursors. Good topological control can be relied upon during the sigmatropic rearrangement, provided that the system is free of transition metal impurities. This feature allows for the incorporation of reliable stereochemical predictability into the synthetic design.;With the readily available 1-methylcycloheptatriene as our starting material, dl-pentalenolactone P methyl ester was successfully synthesized in 32 synthetic operations in an overall yield of 0.3%. Our desired tricyclo(3.2.2.0... |
