- INTERMEDIATES FOR THE PREPARATION OF (3R, 4S)-1-(4-FLUOROPHENYL)-3-[(3S)-3-(4-FLUOROPHENYL)-3-HYDROXYPROPYL)]-4-(4-HYDROXYPHENYL)-2-AZETIDINONE
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A method for the preparation of (S)-alcohol oxazolidides of general formula II, in which PG represents hydrogen or a hydroxyl protecting group, such as trimethylsilyl, tert-butyldimethylsilyl, benzyloxycarbonyl, tert-butoxycarbonyl, benzyl, benzhydryl or
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Page/Page column 4-5
(2011/04/14)
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- METHOD OF PRODUCING (3R,4S)-L-(4-FLUOROPHENYL)-3-[(3S)-3-(4-FLUOROPHENYL)- HYDROXYPROPYL)]-4-(4-HYDROXYPHENYL)-2-AZETIDINONE
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Method of producing (3R,4S)-l-(4-fiuorophenyl)-3-[(3S)-3-(4-fluorophenyl)-3- hydroxypropyl)]-4-(4-hydroxyphenyl)-2-azetidinone (ezetimibe) of formula I, in which alcohol-oxazolidide of general formula II, wherein PG is a phenol protecting group, such as a carbonate group, for instance benzyloxycarbonyl or tert-butyloxycarbonyl, or an arylmethyl group, for instance benzyl, benzhydryl or trityl, or a silyl group, for instance tert- butyldimethylsilyl or thexyldimethylsilyl, is silylated by silylation agents in an inert organic solvent in the temperature range of -10 0C to the boiling temperature of the mixture; the obtained silylether-oxazolidide of general formula III, wherein PG is as defined above and X is a silyl group of general formula SiR1R2R3, wherein R1 to R3 are identical or different alkyl groups with 1 to 5 carbon atoms or the phenyl group, is cyclized by action of bis(trimethylsilyl)acetamide and a base in an inert organic solvent in the temperature range of -20 to 40 0C; and, finally, the obtained protected azetidinone of general formula IV, wherein PG is as defined above and Y is hydrogen or the group X as defined above, is deprotected by action of deprotecting hydrogenolytic agents and/or acidic agents in an inert organic solvent.
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Page/Page column 16-17
(2009/12/27)
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