under magnetic stirring after complete solubilisation of the solid the solution was filtered on nalgene 0 2 u03bcm filter and then added with about 10 ml of n hexane until to obtain complete precipitation the obtained crop was separated by filtration and dried with vacuum pump the solid obtained was identified by nmr spectroscopy using a nmr 500 spectrometer solid solubilized in dmso and characterized by ft ir fig6 7 8 and 9 xrpd fig1 and tga fig1 the comparison between infrared spectra of form ii and form i showed a significant difference between the region 3600 2700 cm u2212 1 around 1700 cm u2212 1 and between 1600 800 cm u2212 1 show fig7 8 and 9 the comparison between xrpd spectra of form ii and form i showed a significant difference see fig1 in fact the most characteristic diffraction peaks of form ii are at 6 3 10 6 19 5 and 25 3 degree while those relatives of form i are at 5 75 18 2 and 23 55 degree 7 dimethoxy methyl camptothecin form i undergoes degradation starting from the temperature of 123 38 u00b0 c the step around 100 u00b0 c is due to variation of heating ramp measured by a suitable melting range apparatus mettler tg 50 temperature ramp from 25 u00b0 c to 600 u00b0 c at 20 u00b0 c min see fig1 and confirmed by the.