Image Number 4 for United States Patent #5194635.
In a preferred embodiment, taxol is treated with mesyl chloride to prepare a taxol derivative with a contracted A-ring, which has comparable activity to taxol in a tubulin depolymerization assay, and which shows cytotoxicity against KB cells in a cell culture assay. In an alternate preferred embodiment, taxol is treated with triethyloxonium tetrafluoroborate (Meerwein's reagent) to produce a taxol derivative with an opened oxetane ring. In another alternate preferred embodiment, reaction of taxol with acetyl chloride yields a taxol derivative in which the oxetane ring is opened and the A-ring is contracted. All of the aforementioned products show in vivo activity in KB cell culture assays. Further, the preferred compounds have different in vivo activities, which makes them ideal to form a range of standards for use in biological testing of other compounds.