GB1445794A - Epimerisation process for lactone intermediates for prostaglandins - Google Patents

Abstract

1445794 Tetrahydro - 5 - hydroxy - 4 - (3R- hydroxybut - 1 - trans - enyl) - 2 - oxocyclopentan[b]furan derivatives IMPERIAL CHEMICAL INDUSTRIES Ltd 20 Jan 1975 [18 Feb 1974] 7215/74 Heading C2C Compounds of formula wherein R<SP>1</SP> is a phenyl, naphthyl or tetrahydronaphthyl radical which is unsubstituted or which is substituted by halogen atoms, hydroxy, nitro or phenyl radicals, alkyl, haloalkyl, alkoxy, alkenyl or alkenyloxy radicals each of up to 4 carbon atoms or by dialkylamino radicals each of up to 4 carbon atoms or by dialkylamino radicals wherein each alkyl is of 1-3 carbon atoms, are prepared in a process of epimerization by reacting a corresponding compound of Formula III wherein R<SP>2</SP> is an aroyloxy radical of up to 13 carbon atoms or an alkanoyloxy radical of up to 6 carbon atoms, with an optionally substituted triphenylphosphine or a tri(C 1-8 alkyl)phosphine, an azodicarboxylic acid di(C 1-6 alkyl)- ester and a carboxylic acid in an inert solvent and then hydrolysing the ester intermediate. The examples prepare racemic (3aR, 4R, 5R, 6aS) - 2,3,3a,6a - tetrahydro - 5 - hydroxy - 4- [(3R) - 3 - hydroxy - 4 - (3 - trifluoromethyl and 3 - chlorophenoxy)but - 1 - trans - enyl] - 2- oxocyclopentan[b]furans from the corresponding starting materials of Formula III in which R<SP>2</SP> is 4-phenylbenzoyloxy by reaction with benzoic acid, triphenylphosphine and diethyl azodicarboxylate in THF followed by hydrolysis with K 2 CO 3 .