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Total Synthesis and Stereochemical Assignment of Nostosin B
Xiaoji Wang1, Junmin Feng2,3, Zhengshuang Xu4
1School of Life Science, Jiangxi Science and Technology Normal University, Nanchang 330013, China. professorwxj@163.com.
Abstract:
Nostosins A and B were isolated from a hydrophilic extract of Nostoc sp. strain from Iran, which exhibits excellent tryps inhibitory activity. Nostosin A was the most potent natural tripeptide aldehyde as trypsin inhibitor up to now. Both R- and S-2-hydroxy-4-(4-hydroxy-phenyl) butanoic acid (Hhpba) were prepared and incorporated into the total synthesis of nostosin B, respectively. Careful comparison of the NMR spectra and optical rotation data of synthetic nostosin B (1a and 1b) with the natural product led to the unambiguous identification of the R-configuration of the Hhpba fragment, which was further confirmed by co-injection with the authentic sample on HPLC using both reversed phase column and the chiral AD-RH column.
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