| abstract |
A process for the preparation of a compound of the formula <IMAGE> (I) which comprises deprotonating a carbamate of the formula <IMAGE> (II) in an inert solvent with a selective base, in the presence of a chelate-forming diamine to give a compound of the formula <IMAGE> (III) and then reacting III in an inert solvent, either with an achiral electrophile of the formula (IV) or (V) or with an optionally prochiral electrophile of the formula (VI) GY, (IV) CO2, (V) <IMAGE> (VI) and in the case in which R1 represents an electrofugic leaving group, optionally again electrophilically substituted with the formation of an acyl anion and renewed deprotonation, and in a last step, solvolytically removing the protecting group -CO-NR10R11. |