The total synthesis of senecic and integerrinecic acids, the esterifying acids present in the pyrrolizidine alkaloids senecionine and integerrimine, is described. Methyl 2-methylene-3- acetoxybutanoate and ethyl methylacetoacetate were condensed to give a mixture of cis- and trans-5-rnethyl-2-hepten-6-one-3-carboxylic acids. Hydrolysis of the cyanohydrin of the tram isomer gave (+)-integerrinecic acid, which was resolved by means of the brucine ...
