Patent ID: 6310248
Filing Date: 2001-10-30
Classification: A61P,C07B,C07C,C07D

Abstract:
A process for the enantioselective preparation of a compound of the general formula (Ia) or (Ib) ##STR20##wherein R.sub.1, R.sub.2 and R.sub.3 independently of each other are hydrogen, methyl, methoxy, hydroxy, hydroxymethyl, carbamoyl, sulphamoyl or halogen, and R.sub.4 and R.sub.5 independently of each other are C.sub.1-6 -alkyl, or a salt thereof, which process comprises the steps of:a) enantiosclectively reducing the carbonyl function in a compound of formula (II): ##STR21##wherein R.sub.1, R.sub.2 and R.sub.3 are as defined above, to form an enantiomerically enriched compound of formula (IIIa) or (IIIb): ##STR22##wherein R.sub.1, R.sub.2 and R.sub.3 are as defined above;b) subjecting the compound of formula (IIIa) or (IIIb) to a sigmatropic rearrangement to form a corresponding enantiomerically enriched compound of formula (IVa) or (IVb): ##STR23##wherein R.sub.1, R.sub.2 and R.sub.3 are as defined above;c) subjecting the compound of formula (IVa) or (IVb) to a Baeyer-Villiger oxidation to form a corresponding enantiomerically enriched compound of the general formula (Va) or (Vb): ##STR24##wherein R.sub.1, R.sub.2 and R.sub.3 are as defined above;d) converting the compound of formula (Va) or (Vb) to form the corresponding enantiometrically enriched compound of formula (Ia) or (Ib); ande) optionally converting the compound of formula (Ia) or (Ib) to a salt thereof.