New Synthesis of Oxygen Heterocycles

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In this project, new synthesis of oxygen heterocycles, which are expected to exhibit biological activities, was studied.In chapter 1, synthesis of -diethoxyphosphinyl- -butenolides and their application to the general synthesis of -lactones with , -fused ring systems were described. Cyclosarkomycin and its analogues were easily and efficiently synthesized in few steps from the -phosphono-butenolide and diethly acetal of 2-(formylalkyl)-1,3-dithianes.In chapter 2, new synthesis of -methylene lactones was described. A various kinds of -diethoxyphosphinyl- , -unsaturated carboxylic acids, which were prepared from diethoxy-phosphinylacetic acid and allylic bromides, easily underwent iodo- and selenolactonization to produce -phosphono-iodo and -selenolactones. The Wittig-Horner reaction of the - phosphonolactones with paraformaldehyde provided -methylene- -lactones in good yields. This synthetic methodology was successfully applied to the synthesis of frullanolide, which is a naturally occurring compound.In chapter 3, new synthesis of 3,4-fused coumarins was described. The Witting-Horner reaction of o-hydroxybenzaldehydes with -diethoxyphosphinyl- -butyro-lactone gave 3-(hydroxyethyl)-coumarins in quantitative yields. The coumarins were easily converted into 3-vinylcoumarins by treatment with DBU. The Diels-Alder reaction of the vinylcoumarins with various dienophiles gave functionalized 3,4-fused coumarins.