studies on total synthesis of bioactive natural products chaetomellic acid A, 1,7(Z)-nonadecadiene-2, 3-dicarboxylic acid, 2-( -Carboxyethyl)-3-octylmaleic anhydride, 2-carboxymethyl-3-hexylmaleic anhydride, ostoclide I, sarkomycin, homosarkomycin, secocrispiolide, mitomycin k and mitomycin c