A 4,10 beta -diacetoxy-2 alpha -benzoyloxy-5 beta ,20-epoxy-1-hydroxy-9-oxo-19-nor-cyclopropa[g]tax-11-ene-13 alpha -yl (2R,3S)-3-tert-butoxycarbonylamino-2-hydroxy-3-phenylpropionate dihydrate, and the preparation thereof by crystallisation from a water-alcohol or water-ketone solution...