Semi-synthetic process for the preparation of taxane derivatives

A process for producing a taxane derivative, the process comprising the steps of:

• protecting the free hydroxy group at the C-7 position of a taxane of formula (I):
• wherein, Z is —OH or a protected —OH, G1 and G2 are the same or different and independently a hydroxy protecting group, and
• attaching a side chain to the free hydroxy group at the C-13 position of the taxane of formula (I) to provide a C-13 protected taxane intermediate,
• wherein the steps of protecting and attaching comprise combining the taxane of formula (I) with a first base, a suitable hydroxy protecting agent and a precursor to the side chain wherein the precursor to the side chain is a single isomer of an open chain phenylisoserine protected by a suitable hydroxy protecting agent at the 2′-position such that the resulting C-13 protected taxane intermediate has a suitable hydroxy protecting agent at the C-7 position and the 2′-position on the phenylisoserine side chain, and
• wherein the taxane of formula (I) and the precursor to the side chain are attached by a condensation reaction carried out at a temperature of 40 to 70° C. in the presence of a mixture of toluene and tetrahydrofuran, a carbodiimide condensing agent, and a catalytic amount of a second base, such that the resulting C-13 protected taxane intermediate has a suitable hydroxyl protecting agent at the C-7 position and the 2′-position on the phenylisoserine side chain.