CRYSTAL-STRUCTURE OF 2-DEBENZOYL, 2-ACETOXY PACLITAXEL (TAXOL(R)) - CONFORMATION OF THE PACLITAXEL SIDE-CHAIN

Crystals of the C2-acetate analog of paclitaxel, grown from a mixture of isopropyl alcohol and methanol, belong to the space group P2(1) wit h a = 9.058(3), b = 18.306(5), c = 15.043(1) Angstrom, beta 97.09(1)de grees, Z = 2, V = 2475.1(9)Angstrom(3), D-calc = 1.269 gcm(-3) and mu = 0.75 cm(-1). The structure was determined by direct methods and refi ned to R(F) = 0.054 and wR(F) = 0.057 for 605 variables and 3496 obser ved reflections. The paclitaxel side chain possesses a conformation si milar to that observed in the crystal structure of docetaxel (Taxotere (R)). A three dimensional network of hydrogen bonds is formed through solvent molecules and stabilizes the crystal lattice.