A large scale separation of taxanes from the bark extract of Taxus yunnanesis and H-1- and C-13-NMR assignments for 7-epi-10-deacetyltaxol

A large-scale separation of paclitaxel from semi-purified bark extract of T axus yunnanesis was investigated. The chromatographic behavior of paclitaxe l and two close eluting analogues, cephalomannine and 7- epi-10-deacetyltax ol were systematically studied on a C-18 bonded phase column with different mobile phase in reverse phase mode. According to the notably different sel ectivity of the methanol and acetonitrile with water in the mobile phase an d the most important requirement of capacity in preparative chromatography, the optimum suitably mobile phase used in a large-scale isolation of pacli taxel and 7-epi-10-deacetyltaxol on a preparative C-18 column was given. Ce phalomannine was eliminated by ozonolysis and after then separated througho ut a normal phase silica column. The whole large-scale process for high pur ity paclitaxel from the bark extract of Taxus yunnanesis consisted of a pre liminary purification with Biotage FLASH 150i system based on a prepacked n ormal phase silica cartridge followed by using a C-18 Nova-pak(TM) column i n Waters PrepLC(TM) 4000 preparative HPLC system. The structure of 7-epi-10 -deacetyltaxol was elucidated by 2D NMR technologies of TOCSY, DQF-COSY, HM QC and HMBC, etc.