The Total Synthesis Of Three Actived Antalgic Compounds From Dragon's Blood.

Dragon's blood is one of the well-known traditional herbs. It is famous for its wide medicinal applications around the world. Dragon's blood has been clinically used as analgesic in our country for a long time and its total flavonoids display antalgic activity. Cochinchinenin B, Loureirin B and Loureirin A were found as active analgetic compounds in the extraction of dragon's blood. Given our interest in the bioactivity evaluation, an increasing demand for a simple and efficient method related the preparation of compounds to prompted us to develop synthesis of Cochinchinenin B,Loureirin B and Loureirin A to obtain materials for further researches and drug development. Herein, we report the novel total synthesis of Cochinchinenin B for the first time and optimize the synthesis of Loureirin B and Loureirin A.The present research is made up of two parts. First part is the total synthesis of Cochinchinenin B. The novel total synthesis is seven-step procedure included Friedel-Crafts reactions, alkylation, Elbs oxidation, Claisen-Schimidt reaction, catalytic hydrogen transfer reduction, cyclization catalysed by Boron trifluoride diethyl etherate and Clemmensen reduction. The total yield was 1.6%. The natural product 2',5',4-trihydroxy-4'-methoxychalcone was synthesized for the first time, and another two intermediates 2',5',4-trihydroxy-4'-methoxydihydrochalcone and 6-hydroxy-3-(4- hydroxybenzyl)-7-methoxychromone were new compounds. The second part of the research was the optimization of the synthesis of Loureirin B and Loureirin A. The two compounds shared the same framework of structure, and the reported synthesis routes of them had the general reaction conditions and schemes. They were synthesized with 4-hydroxyacetophenone as the started material by the reactions step by step as follow: alkylation with benzyl chloride, Claisen-Schimidt reaction, catalytic hydrogen transfer reduction with Hydrogen. The aim of the optimization of the synthesis routes was to reduce the cost and made the art of synthesis simple and convenient. 1,3-Dimethoxyb- enzene benzene and 1,3,5-trimethoxybenzene were converted into relevant substituted benzaldehyde accompanied by DMF and Phosphorus oxychloride. The reductions of the responded chalcones were by catalytic hydrogen transfer reduction with Ammonium formate.The present study describe a novel total synthesis route of Cochinchinenin B for the first time, and optimization of procedures to prepare Loureirin A and Loureirin B, which provide convenient pathway to prepare homoisoflavonoids, dihydrochalcones and their derivatives. Especially, total synthesis of Cochinchinenin B establishs a appropriate platform to prepare mutli-phenolic homoisoflavonoids, which has been regarded as the aporia in total synthesis of natural flavonoids for a long time.