The enantioface-differentiating hydrogenation of methyl 3-oxoalkanoate (CH3(CH2)nCOCH2COOCH3, n=0, 6, 8, 10, 12) over the (R,R)-tartaric acid–NaBr–modified Raney nickel catalyst ((R,R)-TA–NaBr–MRNi) gave methyl (R)-3-hydroxyalkanoate (CH3(CH2)nCH(OH)CH2COOCH3, n=0, 6, 8, 10, 12) in an average optical yield of 85%. After the methyl ester had been converted to dicyclohexylammonium salt of 3-hydroxyalkanoic acid, the salt was recrystallized three times from acetonitrile and then treated with acid to give optically pure (R)-3-hydroxyalkanoic acid (CH3(CH2)nCH(OH)CH2COOH, n=0, 6, 8, 10, 12) in a reasonable yield. From the hydrogenation product with (S,S)-TA–NaBr–MRNi, optically pure (S)-3-hydroxyalkanoic acid was obtained by the same process as above.
The enantioface-differentiating hydrogenation of methyl 3-oxotetradecanoate over (R,R)-tartaric acid-NaBr-modified nickel gave methyl (R)-3-hydroxytetradecanoate(III) in 85% e.e.. After HI was converted to dicyclohexylammonium salt of 3-hydroxytetradecanoic acid (I), the salt was recrystallized three times from acetonitrile and was then treated with acid to give optically pure (R)-I in a good yield.
Nach einem bereits beschriebenen Verfahren wird aus Raney‐Nickel, Natriumbromid und (R,R)‐Weinsäure in wäßriger Lösung ein stereoselektiver Katalysator hergestellt, mit dessen Hilfe die Hydrierung von 3‐Oxotetradecansäuremethylester (I) zu (R)‐3‐Hydroxytetradecansäuremethylester (II) gelingt.
Zur Darstellung der biologisch bedeutenden R‐ bzw. S‐konfigurierten Titelverbindungen (VI) werden die Säurechloride (I) mit der methylenaktiven Verbindung (II) zu den Derivaten (III) kondensiert, deren 1,3‐Dioxanring durch Methanolyse gespalten wird.
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