SYNTHETIC APPLICATIONS OF CARBENE COMPLEXES

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One of the major goals of the proposed work is to develop the asymmetric reactions of chiral imidazolidinone carbene complexes. These complexes will be utilized as chiral acetate equivalents in aldol reactions with alkynals in the synthesis fostriecin, a new anti cancer drug that Is in phase I of human clinical trials. The unusual stereochemistry observed in the aldol reactions with alkynals may be due to a substrate directable aldol reaction. Experiments are proposed to test this and to determine if directable aldol reactions are possible with functional groups other than alkynes. Early results reveal that the imidazolidinone carbene complexes are exo selective in their Diels-Alder reactions and thus a general study is proposed to examine the scope and mechanism of these reactions. The Michael additions of these complexes will also be studied in cases where the chiral carbene complex is to serve both as the Michael acceptor and donor. Applications are proposed for the synthesis of methynolide and dendrobine. The cyclopropanation reactions of Fischer carbene complexes will be investigate for new methods for the synthesis of cyclopropanone acetals and for the asymmetric synthesis of helenalin and cyclopropane amino acids. Also to be explored is a new method for the synthesis of 5- hydroxyindoles from a metal-mediated Bergman type cyclization. Plans are outlined for the development of several asymmetric reactions of carbene complexes with alkynes which include asymmetric benzannulations, asymmetric synthesis of cyclehexadienones and asymmetric synthesis of biaryls. The asymmetric benzannulations with chiral propargyl amines is proposed as the key step in a synthesis of the M(5-7) tripeptide portion of vancomycin. Finally, the reactions of chiral carbene complexes with alkynes will be investigated for the asymmetric synthesis of hydrindenone derivatives and tri- and bicyclic lactones.