Acylation of paclitaxel (I) with 2,3-O-isopropylideneglyceryl chloroformate (II) produced the 2',7-bis-carbonate (III). Subsequent acid hydrolysis of the acetonide groups of (III) furnished the corresponding bis-(dihydroxypropyl)carbonate (IV). The 2'-ester of (IV) was then selectively hydrolyzed using a phosphate buffer at pH 6.5.
In an alternative method, paclitaxel (I) was acylated with allyl chloroformate (V) to afford the bis-carbonate (VI). Dihydroxylation of both allyl groups of (VI) was accomplished by treatment with tert-butyl hydroperoxide producing (IV). The 2'-ester of (IV) was finally removed upon stirring in a NaHCO3-neutralized solution at room temperature.