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3. Yoshikawa, M.; Fukuda, Y.; Taniyama, T.; Kitagawa, I. Chem. Pharm. Bull. 1986, 14, 1403.
4. X-Ray analysis was performed on a Rigaku AFC7R diffractometer with graphite monochromated Mo-Kα radiation and a 12 kW rotating anode generator.
5. Plant material. Scrophularia buergeriana Miq. was collected from Changbai mountains in Jilin province, China, in 1996.