Studies on total synthesis of bioactive natural products chaetomellic acid A 1 7_Z_ _nonadecadiene_2 3_dicarboxylic acid 2_ _Beta_carboxyethyl_ _3_octylmaleic anhydride 2_carboxymethyl_3_hexylmaleic anhydride nostoclide I sarkomycin homosarkomycin secocrispiolide mitomycin K and mitomycin C
