Patent ID: 7157590
Filing Date: 2007-01-02
Classification: C07C

Abstract:
1. A process for the preparation of compound of Formula (1b) wherein R 6 is selected from the group consisting of alkoxy and alkylamino; such process comprising: (a) stereoselective reduction of the carbonyl group of the compound (4) to yield a mixture of compounds of formulae (5a) and (6a), where (5a) is the predominant isomer, which are subsequently converted into a mixture of compounds of formulae (5) and (6): where one of R 1 and R 2 is an arylcarbonyl group and the other one is selected from the group consisting of arylcarbonyl, acyl, trialkylsilyl, dialkylarylsilyl, 1-alkoxyalkyl, unsubstituted and alkyl-substituted tetrahydro-2H-pyran-2-yl and tetrahydrofuran-2-yl; followed by isolation of the compound (5) from the mixture; (b) converting compound (6) from the mother liquor of step (a) into compound (6a), oxidizing the hydroxyl group of the compound (6a) to yield the compound (4) and recycling the compound (4) to step (a); (c) reducing the compound (5) with diisobutylaluminum hydride while maintaining the reaction mixture temperature in the range of from −20° C. to +20° C. followed by hydrolysis of the obtained reaction mixture under basic conditions to give the compound (11), wherein R 3 is hydrogen when R 1 is acyl and is equal to R 1 when it is trialkylsilyl, dialkylarylsilyl, 1-alkoxyalkyl, unsubstituted or alkyl-substituted tetrahydro-2H-pyran-2-yl or tetrahydrofuran-2-yl; R 4 is hydrogen when R 2 is acyl and is equal to R 2 when it is trialkylsilyl, dialkylarylsilyl, 1-alkoxyalkyl, unsubstituted or alkyl-substituted tetrahydro-2H-pyran-2-yl or tetrahydrofuran-2-yl; (d) reacting compound (11) with a metal salt of 5-(triphenylphosphoranylidene)pentanoic acid, to obtain the compound of formula (1a) and (e) alkylation or amidation of the carboxyl group of compound (1a), optionally, after deprotecting the hydroxyl groups, to give the desired compound (1b).