摘要:
Conversion of eta4-cycloheptatriene-Fe(CO)2P(OPh)3 to ketocycloheptadiene-Fe(CO)2P(OPh)3 complex 7 was accomplished by hydroboration followed by Swern oxidation. Methylation and hydroxylation of the enolate from 7 proceeds with complete stereoselectivity, anti to the metal moiety, and introduction of two methyl or hydroxyl groups at the alpha and alpha' positions was accomplished in high overall yield. Reduction of the ketone group on these complexes occurs with high stereoselectivity and is controlled by the boat conformation adopted by these complexes. The product of these reaction sequences were demetalated to give cycloheptadiene derivatives that were further functionalized to give a C(9)-C(14) subunit of calyculin A1 and a C(19)-C(25) subunit of swinholide A.