Studies On Synthesis Of A New Dihydrobenzofuran Neolignans

Lignan compounds, kinds of natural products, are the oxidation polymer ofphenylpropanoids and have unique pharmacological activity, widely distributed innature. For their novel chemical structure, a plurality of chiral center and rich functiongroups, they became the focus of the chemists. Among them, the benzofuranneolignans and the8-5’ neolignans, with wide range of physiological andpharmacological activity, are also widespread on earth. In this paper, we focus on thetotal synthesis of benzofuran neolignan Boehmenan H, which was firstly synthesized,and the study on the synthesis of the8-5’ neolignan and the ring-opening reaction ofthe dihydrobenzofuran neolignan was explored. This paper includes the followingthree parts:Part one is the summery, we introduced the current study status and researchprogress of lianan compounds about its classification, biological activities andphysicochemical properties. This section expound about the research on synthesis ofthe natural neolignans related in this thesis. Then we put forward the research topiccombined with the current research situation.The second part introduced the first total synthesis of benzofuran neolignanBoehmenan H. We used cheaper vanillin and DEM as raw materials, thoughKnoevenagel reaction to get the ferulic acid ethyl ester. In the presence of silver oxide,a biomimetic oxidative coupling of the ferulic acid ethyl ester is the crucial step in thesynthesis sequence to generate the benzofuran skelenten, followed by the firstreduction with LiAlH4and AlCl3, the protection of hydroxyl group with DHP and thesecond reduction with LiAlH4to obtain the intermediate monol. The monol wascondensated with the derivative of ferulic acid, to obtain the latent target compound,after the protecting group was removed, the target compound was obtained.Part three, the research on ring-opening reaction of a synthesis intermediate dihydrobenzofuran neolignan under base conditions was described. These reactionsfully prove that benzofuran ring is very unstable under alkaline conditions, realize thetransition from benzodihydrofuran new lignin to8-5’ neolignan compounds.