third elution solution the above mentioned third elution solution is introduced into a high pressure liquid phase chromatography inverted phase preparation chromatography at pressure of 5 mpa 15 mpa to be separated and purified the high pressure liquid phase chromatography adopts a c 18 chromatographic column of 21 2 mm 250 mm and 5 u03bcm the mobile phase is a 60 wt methanol aqueous solution and the flow rate of the mobile phase is 12 ml min the detection wavelength of the ultraviolet detector is 374 nm the third elution solution is sampled for 60 u03bcl 150 u03bcl at each time the elution solution corresponding to the chromatographic peak retention time of 31 min after the sampling at each time is collected and after solvent is removed the compound of formula i after being obtained the compound of the formula i can be re dissolved in the methanol solution the methanol solution is used as the mobile phase the chromatographic separation can be carried out through a gel column and the compound of the formula i can be further purified the compound of the formula i is yellow powder and the main structure characteristic peaks of an ultraviolet spectrum an infrared spectrum and a hydrogen nuclear magnetic resonance spectroscopy of the compound of formula i are listed hereinafter the ultraviolet spectrum the solvent is methanol u03bb max log u03b5 210 4 36 266 3 82 374 3 68 nm the infrared spectrum potassium bromide pellet u03bd max 3452 2924 2615 1668 1612 1516 1437 1316 1247 1182 1083 1022 868 722 cm u2212 1 1 h nmr 500 mhz cdcl 3 ppm u03b4 10 7 s u2014 oh 9 48 s u2014.