R3 and R5 are identical or different and each represents hydrogen, a straight chain, branched or cyclic alkyl radical having up to 6 carbon atoms, a phenyl or benzyl radical, or one of the substituents R3 or R5 represents an alkyl radical which has up to 6 carbon atoms and is substituted by acetoxy or benzoyloxy, alkoxy or dialkoxy, each having {HEAD ~ up to 3 carbon atoms} in each alkyl group, hydroxyl, {TAIL ~ amino} or aminoalkoxy having up to 6 carbon atoms, or represents the formyl or nitrile group, 
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R3 and R5 are identical or different and each represents hydrogen , a straight chain , branched or cyclic alkyl radical having up to 6 carbon atoms , a phenyl or benzyl radical , or one of the substituents R3 or R5 represents an alkyl radical which has up to 6 carbon atoms and is substituted by acetoxy or benzoyloxy , alkoxy or dialkoxy , each having { HEAD ~ up to 3 carbon atoms } in each alkyl group , hydroxyl , { TAIL ~ amino } or aminoalkoxy having up to 6 carbon atoms , or represents the formyl or nitrile group ,
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