vacuum the aqueous layer is extracted twice with dichloromethane 2 u00d7 20 ml and the organic phase back extracted with water 20 ml then discarded the combined aqueous layers are extracted with a dichloromethane ethanol 1 1 mixture until complete extraction of thiocolchicoside the organic layer is washed with 20 nacl solution 30 ml then the solvent is replaced with methanol and concentrated to 15 ml and left to crystallize under stirring for 2 h at room temperature the product is collected by filtration 2 03 g of 3 o u03b1 l rhamnopyranosyl 3 o demethylthiocolchicine are obtained 78 yield mp 254 5 u00b0 c 1 h nmr dmso d 6 u03b4 ppm 1 19 3h d j 6 6 hz 1 87 1h m 1 88 3h s 2 04 1h m 2 22 1h m 2 44 3h s 2 61 1h m 3 35 1h m 3 59 3h s 3 70 1h m 3 71 1h m 3 85 3h s 4 35 1h m 4 82 1h d j 5 7 hz 4 94 1h d j 5 7 hz 5 12 1h d j 4 3 hz 5 39 1h d j 1 8 hz 6 88 1h s 7.