Synthesis Of Natural Butanolides Isolated From Litsea Akoensis

The compounds that possess an ?-alkylidene-?-hydroxy-y-methyl-y-lactone moiety were isolated from the stem bark or leaves of Litsea akoensis.This paper develops a synthetic route for these natural butanolides.Among them,Litseadioxanins A and B,so far only known natural products with a dihydrodioxine ring at the terminal of a side chain,were synthesized for the first time.The peroxy functionality was installed via a photo[4 + 2]cycloaddition of O2 to a multifunctional terminal 1,3-diene,a subtype of the reaction that has only a limited number of simple precedents(monofunctional/with a much shorter alkyl chain)in the literature to date.LED was found to be superior to traditional mercury or tungsten lamps,not only giving better yields but also significantly simplifying the operations.The diene precursors(also natural products)to Litseadioxanins were also synthesized for the first time.With the aid of the synthetic samples the previously unknown concentration/time-dependence of[?]D of these dienes was revealed.In addition,the compound 1-5 obtained from the leaves of all three species of Hortonia(H.angustifolia,H.floribunda,H.ovalifolia)was first synthesized through this route.