Biologically important and structurally unique marinenaturalproducts avarone (1), avarol (2), neoavarone (3), neoavarol (4) and aureol (5), were efficiently synthesized in a unified manner starting from (+)-5-methyl-Wieland-Miescher ketone 10. The synthesis involved the following crucial steps: i) Sequential BF(3)Et(2)O-induced rearrangement/cyclization reaction of 2 and 4 to produce 5 with complete stereoselectivity
O-induced cascade epoxide-opening/rearrangement/cyclization reaction to stereoselectively construct the requisite pentacyclic ring system in one step. In order to rationalize the mechanism of the cascade reaction, quantum chemical calculations of the possible intermediary carbocations and transition states in the model synthesis were carried out. An alternative approach to synthesize (+)-stachyflin by