| Abstract: | Paclitaxel, an antitumor drug effective on ovarian and breast carcinomas, is currently being produced both by direct isolation from the bark of Taxus brevifolia and by semi-synthesis from a natural precursor, 10-deacetyl baccatin III. Although other potential precursors such as 10-deacetyl paclitaxel-7-xyloside were known since 1984, their conversion to paclitaxel could not be achieved because of the lack of suitable methodology for hydrolyzing the xylose residue, compatible with the stability of the compound. A method is described here using periodate, followed by phenylhydrazine, to effect deglycosidation of 10-deacetyl paclitaxel-7-xyloside to form 10-deacetyl paclitaxel. In addition, by including an intermediate acetylation step before the reaction with phenylhydrazine, “direct” conversion of this xyloside to paclitaxel itself, is described. Because 10-deacetyl paclitaxel-7-xyloside occurs at >0.1% in the bark of Taxus brevifolia, its successful hydrolytic conversion to paclitaxel represents an extremely important reaction for the enhanced availability of this drug. |
