cyclobutane partial structure, which was identified from the typical CH coupling constants ('J = 140-145 Hz) in the coupled 13C-NMR spectrum. In the C,H COLOC diagram, the connectivity of all six carboxyl C atoms (6 = 164.7-174.7) is clearly revealed by the two-and three-bond coupling constants 'JCH and 3JcH, respectively. Accordingly, tropane rings A and B are linked as mesaconic diester D. Further cross signals in the C,H COLOC diagram show that a 2-methyl-4-phenylcyclobutane-1,2,3-tricarboxylic ester E is present, whereby the carboxylic acid function on C 1 forms an ester linkage with the third 3,6-dihydroxytropane C at its 3-hydroxyl group. Furthermore, the C,H COLOC diagram reveals an angelic ester partial structure F, which is linked to tropane ring C through the 6-hydroxyl group. Combination of all partial structures gives the constitution of grahamine (l), which accounts for the twenty double-bond equivalents.The relative configuration of the 0-acyl groups on the tropane rings may be derived from the HH coupling constants. All signals of protons in a 3-position are split into a doublet of doublets (3JHH = 4-5 Hz) owing to coupling with the pseudo-axial protons 2-H and 4-H (interplanar angle ca. 60"). Signal broadening occurs as a result of unresolved HH coupling to the pseudo-equatorial protons in 2-and 4-positions (interplanar angle ca. 90°). Accordingly, the 3-H protons are pseudo-equatorial and the 3-0-acyl groups pseudoaxial. The signals of the 6-H protons are each a doublet of doublets with 3JHH = 7.8-8.8 Hz to 7-H,,,, and 3.5-3.8 Hz to 7-H,,,. Further couplings with 5-H are again unresolved (interplanar angle nearly 90"); examination of the interplanar angle between the protons 5-H and 6-H in a Dreiding model reveals that only 6-H in endo position allows an interplanar angle to 5-H of about 90". Thus, the 6-0-acyl groups are exo. The CH coupling constants of the carboxyl C atoms at 6 = 166.3 (D) and 167.7 (F) reflect the relative configuration c', VCH Verlagsgesellschafi mbH. D-6940 Weinhelm. 1990 0570-0833I90j0404-0386 3 02.SOj0Angew. Chem. Inr. Ed. Engl. 29 (1990) No. 4

Key synthons to the title compounds are optically active y -lactones with known or experimentally determined absolute configurations. Horse liver alcohol dehydrogenase, which catalyses the oxidation of mesoand racemic non-meso diols to chiral lactones, and pig-liver esterase, which catalyzes the saponification of meso-diesters to chiral half-esters, were utilized for the asymmetric synthesis of such precursors. The racemic non-meso diol rac-l is converted to the two stereoisomeric y-lactones (+)-2 and (+)-3 which are readily separated. meso-Diol 12 is oxidized to the chiral y-factone (-)-11. Its enantiomer (+)-11 is obtained by enantioselective saponification of the meso-diester 9 with pig-liver esterase. Appropriately designed syntheses lead from these chiral intermediates to both enantiomers (+)-and (-)-6 of viridiene and (+)-and (-)-I8 of aucantene. In addition, kinetically controlled reduction of the racemic aldehydes racda and rac-15 with horse liver alcohol dehydrogenase offers a convenient alternative to the enantioselective preparation of the enantiomers of the two hydrocarbons 6 and 18. Chromatography of 6 on triacetylated cellulose as a stationary chiral phase confirms the enantiospecificity of the synthetic routes designed.

No abstract

Abb. 3. Struktur des Addukts 4 im Kristall; &! ) = Si [lo]. durch Verwendung von 1,2-Dihydrocyclobutabenzolkomplexen mit andern ML,-Resten, durch die Anwendung milderer Ringoffnungsbedingungen und/oder durch alternative Wege zu n-komplexierten ortho-Chinodimethankomplexen iiberwunden werden. Experimentelles Das Diastereomerengemisch von syn-2 und anti-2 (70%) aus dem Arenaustausch mit Tricarbonyl(naphtha1in)chrom wurde durch Flashchromatographie mit HexanjEther 4/1 getrennt 1 (syn-2: R, = 0.13, anti-2: R, = 0.19). syn-2: Fp(Hexan) = 59-60"C. IR(Hexan, v(C0)): C[cm-'] = 1984(s), 1918(s). 'H-NMR (360 MHz, C,D,): 6 = 1.18 (t, 3H, J = 7 Hz; CH,), 2.60 (dd, 1 H, J = 5.5,14Hz;H,,,,-CZ),2.86(dd,lH,J= 1.5,14Hz;H,,.-C2),3.18-3.46(m, 2H;OCH,CH3),4.12(t,1H,J=6Hz;H.,.,),4.20(dd,1H,J=2,5.5Hz; CHOCH,CH,), 4.46 (t. 1 H, J = 6 Hz; H.,,,), 4.52 (d, 1 H, J = 6 Hz; Hare,,), 4.83 (d, 1 H, J = 6 Hz; anti-2: Fp(Hexan) = 71.5-72.5"C. IR (Hexan, v(C0)): C[cm-'] = 1984(s), Korrekte Elementaranalyse. Angew. Chem. 102 (1990) Nr. 4 Q VCH l+rlagsgesellschaft mbH. D-6940 Weinheim, f990 0044-8249/90/0404-0425 $02.50/0

The possibility of using the enzyme (R)-Oxynitrilase in a biphasic lyotropic liquid crystal/dibutylether system has been demonstrated. This reaction system is applicable for the continuous production of (R)-benzaldehydecyanohydrin in a fixed bed reactor. The optical purity was between 94 and 96% ee and independent of the flow rate. The space time yield was maximal (2650 g/(l* d)) at a flow rate of 1.6 ml/min. KEY WORDSEnzymatic synthesis, oxynitrilase, chiral cyanohydrin, organic solvents, lyotropic liquid crystals. t To whom all correspondence should be addressed 61 Biocatal Biotransformation Downloaded from informahealthcare.com by University of Newcastle on 01/05/15 For personal use only. Biocatal Biotransformation Downloaded from informahealthcare.com by University of Newcastle on 01/05/15 For personal use only. Table 1 Kinetic constants of (R)-Oxynitrilase in citrate buffer pH = 3.75, T = 20°C and cubic liquid crystals buffer liquid crystals u,,,