Selective synthesis of 14β-amino taxanes

The base induced deprotonation of H-14 of 7-triethylsilyl- (7-TES-) and 7-tert-butoxycarbonyl- (7-BOC-) protected 13-oxobaccatins gave the corresponding enolates, which were selectively aminated with electrophilic nitrogen donors, such as azodicarboxylates and tosyl azide. In particular, tosyl azide gave the corresponding 7-BOC- and 7-TES-13-oxo-14 beta-azido-baccatin III. Alternatively, the last compound was prepared via NaN3 induced azidation of the 13-silyl enol ether of 7-TES-13-oxo-baccatin III under oxidative (cerium ammonium nitrate) conditions. The 13-silyl enol ether was obtained in a multistep process by DBU induced silylation of 7-TES-13-oxobaccatin III. The 7-TES-13-oxo-14 -azido-baccatin III was used as a key intermediate for the synthesis of a new family of antitumour taxanes containing amino based functional groups at the C-14 position, such as: 14 beta-azido, 14 beta-amino, 14 beta-amino 1, 14-carbarnate, 14 beta-amino 1, 14-thiocarbamate, and 14 beta-amino N-tert-butoxycarbonyl- 1, 14-carbarnate. (c) 2005 Elsevier Ltd. All rights reserved.