Patent ID: 6417382
Filing Date: 2002-07-09
Classification: C07C

Abstract:
A process for preparing a compound of the formula (I) whereinR1 denotes a group selected from among methyl, ethyl, propyl, cyclopentyl, cyclohexyl, phenyl, benzyl and â€”C(Me2)phenyl, each of which is optionally mono-, di- or trisubstituted by hydroxy; R2 denotes a group selected from among methyl, ethyl, propyl and benzyl, which process comprises the following steps: (a) reacting a compound of the formula (II) whereinR1â€² denotes a group selected from among methyl, ethyl, propyl, cyclopentyl, cyclohexyl, phenyl, benzyl and â€”C(Me2)phenyl, each of which is optionally mono-, di- or trisubstituted by a group â€”Oâ€”PG, the group â€”Oâ€”PG denoting a protected hydroxyl function selected from among methoxymethyloxy, 2-methoxyethoxymethyloxy, 1-ethoxyethyloxy, 2-tetrahydropyranyloxy, 1-butoxyethyloxy, tert.-butyloxy, benzyloxy and 4-methoxybenzyloxy, with an alkali metal hexaalkyldisilazane of the formula (VIII) whereinMet denotes an alkali metal, and R3 independently in each case denotes a C1-4-alkyl group; (b) treating the product of step (a) with a compound of the formula (III) R2â€”Oâ€”COXâ€²â€ƒâ€ƒ(III) wherein:R2 is as hereinbefore defined in this claim and Xâ€² denotes chlorine, bromine or â€”Oâ€”R2, wherein R2 is as hereinbefore defined in this claim; (c) treating the product of step (b) with a protic acid of formula HY, wherein Y denotes the counter ion, to yield a compound of the formula (IV) or a tautomer thereof, wherein the groups R1, R2 and Y are as hereinbefore defined in this claim;(d) isolating the compound of the formula IV produced in step (c); (e) treating the isolated compound of the formula IV, produced in step (d) with a base to produce the compound of the formula I.