I.~Biosynthesis of tropic acid. II.~Determination of the absolute and relative configuration of mycotoxin, fumonisin B(1).

摘要

(S)-Tropic acid is the aromatic acid moiety of the medicinally important alkaloids hyoscyamine and scopolamine. By means of appropriately labeled precursors it has been proven that phenylalanine is the precursor of tropic acid in Datura plants. We have observed the 1,2-carbonyl rearrangement behavior of several model compounds under free radical and anionic conditions in an effort to obtain some information of the possible mechanism for the phenylalanine to tropic acid rearrangement. The experiments conducted under free radical conditions revealed no rearranged products for three of the model compounds used. However, under anionic conditions, e.g., samarium iodide and sodium naphthalenide, 1,2-carbonyl rearrangement products accounted for the majority of the material isolated from each reaction. Reductions carried out with sodium naphthalenide furnished 1,2-carbonyl migration products in which the thioester migration was preferred. These results can be contrasted with the samarium iodide reductions in which both the thioester and carboethoxy migration products were observed. Comparable results were obtained under free radical and anionic conditions for the other two model compounds studied. Lastly, no evidence of rearranged products was observed for the organocobalt model system, even though evidence for free radicals was substantiated from the observed trapped product isolated from the reaction. Most importantly, we have discovered, to our knowledge, the first 1,2-carbonyl migration promoted by a lanthanide reagent, i.e., samarium iodide.;Fumonisin B