| Fortuneanoside E (3,4’-dihydroxy-3’,5’-dimethoxy-(1, 1’-diphenyl)-4-O-β-D-glucopyrano-side) was isolated from the fruit of pyracantha fortueana and was found to show potent in vitro tyrosinase inhibitory activity. Although several methods for the construction of Biphenyl in the synthesis of non-natural compounds have been reported, studies towards total synthesis of the Fortuneanoside E have never been documented. Fortuneanoside E has been prepared from readily available starting materials 3-bromophenol through formylation, protection of Ar-OH group, Suzuki reaction with commercially available 3,4,5-trimethoxyphenylboronic acid, Baeyer-Villiger oxidation, hydroylysis, glycosylation with 2,3,4,6-tetra-O-benzoyl-D-glucopy-ranosyl trichloroacetimidate, selective demethylation and debenzylation. In summary, we have completed an efficient total synthesis of Fortuneanoside E with 8 steps and an overall yield of 16.1%.Meanwhile we developed a new selective demethylation and debenzylation with MgI2 under solvent-free condition. The substrate scope was investigated and included a variety of aryl ethers featuring methoxy and/or benzyloxy groups. These are characters of this method:1) Compared to the conventional demethylation and debenzylation methods at reflux, solvent-free conditions could not only accelerate the reaction, but also realize the transformation that could not take place under conventional reflux conditions; 2) Selective debenzylation could be realized when both functional groups were present in one molecule; 3) A variety of functional groups including COCH3, COOH, COOC2H5, benzoyl as well as glucosidic were tolerated under the reaction conditions.Besides, a rapid and efficient method for the synthesis of MgI2 was developed. The conventional synthesis of MgI2 often requires several hours. Taking care to protect the reaction from light, it only took a few minutes for the reaction between Mg and iodine in dry ether to be complete under ultrasound irradiation. |
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