Patent ID: 7161008

Claim:
A process for preparing a compound of formula (III) or its diastereoisomer wherein R 1 is hydrogen; tert-butyl; or aryl or heteroaryl; R 2 , R 3 and R 4 are each, independently, hydrogen; (C 1 –C 7 )alkyl, optionally substituted by aryl; (C 3 –C 7 )cycloalkyl; or aryl or heteroaryl; R 5 is aryl or heteroaryl; and Y* − is the conjugated base of an optically active, organic Brønsted acid, provided that R 1 and R 4 are not concurrently present as hydrogen, comprising reacting compounds of formulae (IV), (V), (VI) and (VII) wherein R 1 , R 2 , R 3 , R 4 and R 5 are as defined in the present claim, and HY* is the optically active, organic Brønsted acid, without a solvent or in one or more suitable solvents, (i) simultaneously in a direct Mannich reaction, or (ii) sequentially wherein initially the compounds of formulae (IV) and (V) are reacted to give an imine of formula (X) or an aminal of formula (XI), either of which is optionally isolated, and then reacting the compound of formula (X) or (XI) with the compounds of formula (VI) and (VII).