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Lipase‐catalyzed ring‐opening polymerization of 10‐fluorodecan‐9‐olide (1a), 11‐fluoroundecan‐10‐olide (1b), 12‐fluorododecan‐11‐olide (1c) and 14‐fluorotetradecan‐13‐olide (1d) gave optically active products with Mw of 3.000 to 8.000, while 10‐fluoroundecan‐11‐olide (3a) gave an optically inactive polymer with Mw = 11.000. On the other hand, Candida antarctica lipase‐catalyzed polymerization of 10‐ to 14‐membered ω‐fluoro‐(ω‐1)‐hydroxyalcanoic acids gave optically inactive oligomers with Mw of 3.000 to 11.000 in the presence of molecular sieves, while reactions without molecular sieves gave oligomers with lower molecular weight, but with small optical rotations. 9‐Fluoro‐10‐hydroxydecanoic acid, on the other hand, gave an optically inactive polyester with Mw = 7400. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2004–2012, 2000

The chemoenzymatic synthesis of the racemate and the one enantiomer of the fluorinated analogue 8 of the natural cyclooxygenase inhibitor lasiodiplodin is decribed. A lipase-mediated deracemization of the fluorohydrin 18 provided the chiral, nonracemic building block for the enantioselective synthesis of the title compound. The key step was the formation of the 12-membered lactone by a ring-closing metathesis.

. Thermolysis of 3 leads to the formation of an equilibrium mixture of the 4,5homotropilidenes 5 and 6. According to NMR measurements and AM1 calculations the formation of 6 is strongly favored. An equilibrium between 4,5homotropilidene complexes is significantly different from that of the metal-free ligands. By the reaction of 5/6 with bis(ethy1ene)rhodium 1,3-pentanedionate (8) the complexes 9 and 10 of both 4,5-homotropilidenes 5 and 6 are obtained in a 1:3 ratio. The (1,5-diene)rhodium(I) complexes 9 and 10 are nonfluxional and configurationally moderately stable at 20°C. The reaction of 5/6 with Fez(C0)9 gives the n-allyl,o complexes 11 and 12 in a 10:3 ratio, both of which may be derived from the minor 43-homotropilidene isomer 5. In 11 a vinylcyclopropane unit of 5 serves as a four-electron donor for a Fe(C0)3 group. In 12 the 4,5homotropilidene unit is coordinated as a six-electron donor to a Fe2(C0)6 unit. Eine Cyclopropanierung speziell der terminalen C = CBindung von l-Metalla-l,5,7-trienen ist aus geometrischen Griinden nur dann moglich, wenn die mittlere C=C-Bindung die cis-Konfiguration aufweist. (Cycloheptatrienylmethy1)carben-Komplexe 3 erfiillen diese Voraussetzung, da alle C = C-Bindungen des Siebenrings in der cis-Konfiguration fixiert sind. Wir beschreiben hier zunachst die Darstellung von Komplexen 3 und anschlieI3end deren Thermolyse.

diastereoselective syntheses, enantioselective syntheses diastereoselective syntheses, enantioselective syntheses (incl. cis/trans-isomerism) O 0031 -022Enantioselective Ring-Opening of Epoxides by HF-Reagents. Asymmetric Synthesis of Fluoro Lactones.-The asymmetric ring opening of meso-(I) and racemic epoxides [cf. (III), (V)] with appropriate HF-reagents mediated by Jacobsen's enantiopure (salen)chromium chloride provides optically active fluorohydrines (up to 90% e.e.). This reaction and, more efficiently, a lipase-catalyzed deracemization are applied to synthesize enantiopure building blocks (VIII) for the preparation of both enantiomers of a fluorinated analogue of prostaglandin biosynthesis inhibitor lasiodiplodin (XII). -(HAUFE,