Lactones 27 [1]: Transformations of γ-lactones fused to a dimethylcyclohexane ring in Absidia cylindrospora cultures

Two saturated (4a,b) and one unsaturated (5) bicyclic γ-lactones containing a dimethylcyclohexane ring were subjected to biotransformation using the fungal strain Absidia cylindrospora. Six new compounds (6–11) and one known (12) [K.W. Rosenmund, H. Herzberg, H. Schutt, Chem. Ber. 87 (1954) 1258] [2] were isolated. All substrates were stereoselectively hydroxylated by the microorganism at either the C-4 (in the case of 4a and 5) or C-2 position (in case of 4a and 4b) giving the corresponding hydroxylactones with tertiary (6 and 9) or secondary (8 and 10) hydroxy groups, respectively.

The hydroxy group was also introduced into C-3 (in the case of 4a) and C-6 (in the case of 4b) positions. The structures of all obtained products were established on the basis of their spectral data. In the case of lactones 8–10 these structures were undoubtedly confirmed by their X-ray analysis.     

Oxidation of 1,4-alkanediols into γ-lactones via γ-lactols using Rhodococcus erythropolis as biocatalyst

Whole cells of Rhodococcus erythropolis DSM 44534 grown on ethanol, (R)- and (S)-1,2-propanediol were used for biotransformation of racemic 1,4-alkanediols into γ-lactones. The cells oxidized 1,4-decanediol (1a) and 1,4-nonanediol (2a) into the corresponding γ-lactones 5-hexyl-dihydro-2(3H)-furanone (γ-decalactone, 1c) and 5-pentyl-dihydro-2(3H)-furanone (γ-nonalactone, 2c), respectively, with an EE(R) of 40–75%. The transient formation of the γ-lactols 5-hexyl-tetrahydro-2-furanol (γ-decalactol, 1b) and 5-pentyl-tetrahydro-2-furanol (γ-nonalactol, 2b) as intermediates was observed by GC–MS. 1,4-Pentanediol (3a) was transformed into 5-methyl-dihydro-2(3H)-furanone (γ-valerolactone, 3c) whereas (R)- and (S)-2-methyl-1,4-butanediol (4a) was converted to the methyl-substituted γ-butyrolactones 4-methyl-dihydro-2(3H)-furanone (4c₁) and 3-methyl-dihydro-2(3H)-furanone (4c₂) in a ratio of 80:20 with a yield of 55%. Also cis-2-buten-1,4-diol (5a) was transformed resulting in the formation of 2(5H)-furanone (γ-crotonolactone, 5c). At the higher pH values of 8.8 the yield of lactone formed was improved; however, the enatiomeric excesses were slightly higher at the lower pH of 5.2.     

Lactones 26 : Stereoselective microbial epoxidation of unsaturated bicyclic γ-lactones with the alkylsubstituted cyclohexane system

The strain Absidia cylindrospora was chosen among eight fungal strains for the biotransformation of unsaturated lactones 1a–c. The processes were carried out by means of shaken cultures. The compounds 1a and 1b were efficiently converted into the corresponding trans-epoxylactones (2a and 2b), whereas the transformation of 1c gave the unsaturated hydroxylactone 3, with the tertiary hydroxy group introduced in the allylic position. The compound 2b was obtained with 100% ee. The structures of compounds 2a and 2b were fully confirmed by the X-ray analysis, which showed the half boat and half chair conformation of cyclohexane ring in these molecules, respectively. All the products were not reported previously in the literature.     

Alkene rotation in [Ru(η-C5H5) (L2) (η-alkene][CF3SO3] with L2 = iPr- or pTol-diazabutadiene. X-ray crystal structure of [Ru(η-C5H5(pTol-DAB) (η-ethene][CF3SO3]

Reaction of RuCl(η⁵-C₅H₅(pTol-DAB) with AgOTf (OTf = CF₃SO₃) in CH₂Cl₂ or THF and subsequent addition of L′ (L′ = ethene (a), dimethyl fumarate (b), fumaronitrile (c) or CO (d) led to the ionic complexes [Ru(η⁵-C₅H₅)(pTol-DAB)(L′)][OTf] 2a, 2b and 2d and [Ru(η⁵-C₅H₅)(pTol-DAB)(fumarontrile-N)][OTf] 5c. With the use of resonance Raman spectroscopy, the intense absorption bands of the complexes have been assigned to MLCT transitions to the iPr-DAB ligand. The X-ray structure determination of [Ru(η⁵-C₅H₅)(pTol-DAB)(η²-ethene)][CF₃SO₃] (2a) has been carried out. Crystal data for 2a: monoclinic, space group P2₁/n with A = 10.840(1), b = 16.639(1), C = 14.463(2) Å, β = 109.6(1)°, V = 2465.6(5) ų, Z = 4. Complex 2a has a piano stool structure, with the Cp ring η⁵-bonded, the pTol-DAB ligand σN, σN′ bonded (Ru-N distances 2.052(4) and 2.055(4) Å), and the ethene η²-bonded to the ruthenium center (Ru-C distances 2.217(9) and 2.206(8) Å). The C = C bond of the ethene is almost coplanar with the plane of the Cp ring, and the angle between the plane of the Cp ring and the double of the ethene is 1.8(0.2)°. The reaction of [RuCl(η⁵-C₅H₅)(PPh)₃ with AgOTf and ligands L′ = a and d led to [Ru(η⁵-C₅H₅)(PPh₃)₂(L′)]OTf] (3a) and (3d), respectively. By variable temperature NMR spectroscopy the rottional barrier of ethene (a), dimethyl fumarate (b and fumaronitrile (c) in complexes [Ru(η⁵-C₅H₅)(L₂)(η²-alkene][OTf] with L₂ = iPr-DAB (a, 1b, 1c), pTol-DAB (2a, 2b) and L = PPh₃ (3a) was determined. For 1a, 1b and 2b the barrier is 41.5±0.5, 62±1 and 59±1 kJ mol⁻¹, respectively. The intermediate exchange could not be reached for 1c, and the ΔG^# was estimated to be at least 61 kJ mol⁻. For 2a and 3a the slow exchange could not be reached. The rotational barrier for 2a was estimated to be 40 kJ mol⁻. The rotational barier for methyl propiolate (HC≡CC(O)OCH₃) (k) in complex [Ru(η⁵-C₅H₅)(iPr-DAB) η²-HC≡CC(O)OCH₃)][OTf] (1k) is 45.3±0.2 kJ mol⁻¹. The collected data show that the barrier of rotational of the alkene in complexes 1a, 2a, 1b, 2b and 1c does not correlate with the strength of the metal-alkene interaction in the ground state.     

Structural studies on [Mo3S4] and [Mo3S4Cu] complexes with tripodal ligands providing various NxOy (x + Y = 3) donor sets

The interaction of 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) and its N-methylated derivative 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol (tdci) with the incomplete [Mo₃S₄]⁴⁺ cube and the heterometallic [Mo₃S₄Cu]⁴⁺ cube have been investigated by X-ray analysis. The crystal structures of [Mo₃S₄(taci+ rmC₃H₆O-H₂O)₃-4H]·2OH₂O (1a, rhombohedral, space group R32, A = 15.964(3), C = 40.59(1) Å, Z = 6), [Mo₃S₄(tdci)₃]Br₄·9.5EtOH·5H₂O (2a, triclinic, space group

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and [CuBrMo₃S₄(tdci)₃]Br₃·11 H₂O·EtOH (3a, monoclinic, space group P2,/n, A = 14.887(3), B = 22.570(4), C = 21.974(5) Å, β = 98.54(2)°, Z = 4) revealed andN-N-O and an N-O-O coordination mode for taci and tdci, respectively. In 1a, taci is coordinated as an anion with deprotonated oxygen and nitrogen donors. In addition, the non-coordinating amino group reacted with one equivalent; of acetone, forming a Schiff base condensation product. For 2a, short Mo---O bonds and high pK_a values (compared to the aqua ion [Mo₃S₄(H₂O)₉]⁴⁺) indicate the formation of a zwitterionic form of the tdci ligand with coordinated alkoxo groups and peripheral dimethylammonium groups. No significant differences were found for the structural properties of the Mo-tdci fragment in 2a and 3a. The coordination modes of taci and tdci, as observed in the solid state, are in agreement with the previously reported solution structures, established by NMR spectroscopy. They are attributed to the specific steric requirements of the two ligands and to a pronounced preference of the [Mo₃(μS)₃(μ₃S)]⁴⁺ core to coordinate a nitrogen donor trans to μ₃S.     

Preparation of trimethylsilyl alkyne complexes of bis(pentamethylcyclopentadienyl)zirconium, (η-C5Me5)2Zr(RC≡CSiMe3), and their regioselective reactions with nitrous oxide

Benzene solutions of Cp^*₂ZrCl₂ (1) (Cp^* = η⁵-C₅Me₅) react with the alkynes Me₃SiC≡CPh, Me₃SiC≡C(c-C₅H₉) and Me₃SiC≡CCMe₃ in the presence of Na/Hg amalgam to afford high yields of the respective alkyne complexes Cp^*₂Zr(Me₃SiC≡CPh) (2), Cp^*₂Zr{Me₃SiC≡C(c-C₅H₉)} (3) and Cp^*₂Zr(Me₃SiC≡CCMe₃) (4) as crystalline compounds. Complex 2 crystallizes in the triclinic space group with a = 9.791(6), b = 10.466(6), c = 15.756(12) Å, = 86.09 (5), β = 72.09(5), γ = 72.06(4)° and Z = 2. The least-squares refinement converged to R(F) = 0.0604 and R(wF) = 0.0628 for the 3655 unique data with F_o > 4σ (F_o). Salient metrical parameters of the bound alkyne include the following: C(30)-C(31) = 1.340(9) Å; Zr-C(30) = 2.178(6) Å; Zr-C(31) = 2.219(5) Å; C(30)-C(31)-Si = 141.0(5)°; C(31)-C(30)-C(26) = 135.5(5)°. Nitrous oxide reacts with 2 or 3 to afford ((5) R = Ph; (6) R = c-C₅H₉) and 1 equiv. of N₂ via an intermediate, , which is unstable with respect to loss of dinitrogen to give the oxametallacyclobutene derivatives 5 and 6. The oxygen-atom insertion is regiospecific for the Zr-C bond that is attached to the carbyl (Ph or c-C₅H₉) substituent. Under similar conditions, complex 4, in which the alkyne is particularly labile, gives a myriad of products in its reaction with N₂O.     

Preparation, properties and reactions of metal-containing heterocycles Part LXXXIX. Metalla[n]- and metalla[m.n]orthocyclophanes as mediators for the synthesis of cyclic ketones

The reaction of the bis(triflates) 1,2-bis[2-(trifluoromethylsulfonyloxy)ethyl]benzene (1), 1,2-bis[3-(trifluoromethylsulfonyloxy)propyl]benzene (3) and 1,2-bis{2-[2-(trifluoromethylsulfonyloxy)ethyl]phenyl}ethane (6), respectively, with the carbonyl metalates [M(CO)₄]^2- (M=Os (a), Ru (b), Fe (c)) results in the formation of the osmaorthocyclophanes 2a, 4a, 7a and 8a, the ruthenacylophane 2b and the ferracyclophanes 2c and 7c, respectively. Carbon monoxide insertion into the Fe-Cσ bonds of the ferracycles 2c and 7c, respectively, affords the ketones 3-oxo[5]orthocyclophane (9) and 3-oxo[5.2]orthocyclophane (11). The structure of 2a was investigated by an X-ray structural analysis. 2a crystallizes in the monoclinic space group P2₁/n with Z=4.     

Lactones 29 . Enzymatic resolution of racemic γ-lactones

Studies on the application of commercially available enzymes to resolution of the racemic unsaturated γ-lactones: 5-(3-methylbutylidene)-4-methyl-tetrahydrofuran-2-one (1a) and 5-(3,3-dimethylbutylidene)-4-methyl-tetrahydrofuran-2-one (2a) are presented. Lipase PS, Rhizopus niveus lipase, Rhizopus arrhizus lipase, porcine pancreas lipase and hog liver esterase transformed substrates into their respective γ-keto acids with good efficiency (50-75%). Three of them hydrolysed the studied lactones with moderate enantioselectivity. Enantiomeric excesses determined by GC for the unreacted lactones were in the range of 20-60%. Lipase PS preferentially hydrolysed the (+) enantiomers of lactones 1a and 2a whereas R. niveus lipase hydrolysed the (-) enantiomers, respectively.     

Variation in δC values for the seagrass Thalassia testudinum and its relations to mangrove carbon

Carbon isotope ratios (¹³C/¹²C) were measured for the leaves of the seagrass Thalassia testudinum Banks ex König and carbonates of shells collected at the seagrass beds from seven sites along the coast of southern Florida, U.S.A. The δ¹³C values of seagrass leaves ranged from −7.3 to −16.3‰ among different study sites, with a significantly lower mean value for seagrass leaves from those sites near mangrove forests (−12.8 ± 1.1‰) than those far from mangrove forests (−8.3 ± 0.9‰; P < 0.05). Furthermore, seagrass leaves from a shallow water area had significantly lower δ¹³C values than those found in a deep water area (P < 0.01). There was no significant variation in δ¹³C values between young and mature leaves (P = 0.59) or between the tip and base of a leaf blade (P = 0.46). Carbonates of shells also showed a significantly lower mean δ¹³C value in the mangrove areas (−2.3 ± 0.6‰) than in the non-mangrove areas (0.6 ± 0.3‰; P <0.025). In addition, the δ¹³C values of seagrass leaves were significantly correlated with those of shell carbonates (δ¹³C seagrass leaf = −9.1 + 1.3δ¹³C shell carbonate (R² = 0.83, P < 0.01)). These results indicated that the input of carbon dioxide from the mineralization of mangrove detritus caused the variation in carbon isotope ratios of seagrass leaves among different sites in this study.     

Synthesis and characterization of organomolybdenum and organotungsten halides containing the η-pentabenzylcyyclopentadienyl ligand η-Bz5C5M(CO)3X (M = Mo, W; X = Cl, Br, I). The X-ray molecular structure of η-Bz5C5Mo(CO)3I

An improved synthetic procedure for pentabenzylcyclopentadiene Bz₅C₅H was developed. Six new organomolybdenum and organotungsten halides η⁵-Bz₅C₅M(CO)₃X(M = Mo, W; X = Cl, Br, I) were syntesized through the reaction of η⁵-Bz₅C₅M(CO)₃Li (derived from Bz₅C₅H, n-BuLi and M(CO)₆) with PCl₃, PBr₃ or I₂ and characterized by elemental analysis, IR and ¹H NMR spectroscopy. The structure of η⁵-Bz₅C₅Mo(CO)₃I was determined by single-crystal X-ray diffraction techniques. It crystallized in the monoclinic space groupp P2/c with cell parameters a = 13.294(4), B = 15.147(4), C = 19.027(3) Å, β = 108.32(2)°, V = 3637(2) ų, Z = 4 and D_x = 1.50 g cm⁻³. The final R value was 0.035 for 4564 observed reflections.     

Direct nitration of aryl groups σ-bound to ruthenium(II)

A new method has been developed for the preparation of nitroaryl transition metal complexes using copper(II) nitrate in the presence of acetic anhydride (Menke conditions) to directly nitrate an aryl group which is already σ-bound to a transition metal centre. Under these conditions ruthenium(II) aryl complexes of the type: (where R₁=R₂=H; R₁=H, R₂=CH₃; R₁=CH₃, R₂=H) react to yield three distinct types of nitroaryl-containing products (I–III).

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The preparation and characterisation of these compounds are described. X-ray crystallographic data for one example of each of the three types of compound, are also reported. The compounds that have been studied crystallographically are Ru(C₆H₄NO₂-4)(η²-O₂CCH₃)(CO)(PPh₃)₂ (1a), C₄₅H₃₇NO₅P₂Ru·(CH₂Cl₂)_0.5, a = 20.254(5), b=19.437(8), c=22.629(3) Å, β=115.390(10)°, monoclinic, space group C2/c, Z=8; Ru(C6H4N[O]O-2)- Cl(CO)(PPh₃)₂ (4a), C₄₃H₃₄ClNO₃P₂Ru, a=9.331(3), b=12.443(2), c=16.346(3) Å, =82.81(2), β=85.03(2), γ=74.76(2)°, triclinic, space group P , Z=2; Ru(C₆H₂CH₃-2,NO₂-4,N[O]O-6)Cl(CO)(PPh₃)₂ (5b), C₄₄H₃₅Cl- N₂O₅P₂Ru·(CH₂Cl₂)₂, a=19.497(3), b=14.502(3), c=19.340(5) Å, β=122.79(1)°, monoclinic, space group Cc, Z=4.     

Hydride complexes of platinum(II) containing unsymmetrical di(phosphine) ligands: synthesis, characterization and evidence for pairwise addition of hydrogen based on parahydrogen induced polarization

Unsymmetrical di(phosphine) ligands (dpp)₂Rop (1a, b = bis(diphenylphosphino)-2-alkyl-3-oxapropane (alkyl = methyl and ethyl)) and (dpp)₂oCy (1c = trans-2-diphenylphosphinocyclohexyl diphenylphosphinite) and their Pt(II) dichloride complexes, PtCl₂((dpp)₂mop) (2a), PtCl₂((dpp)₂eop) (2b) and PtCl₂((dpp)₂oCy) (2c), have been synthesized and characterized by NMR spectroscopy. The crystal structures of 2b and 2c show that the geometry about the platinum centers is square planar. In 2b, the metal and di(phosphine) ligand chelate ring are in a chair conformation, whereas in 2c, the chelate ring conformation is a skewed boat. Initial reaction of sodium borohydride with 2a, b, c yields the monohydride monochloride complexes PtHCl((dpp)₂mop) (5a), PtHCl((dpp)₂eop) (5b) and PtHCl((dpp)₂oCy) (5c). At longer reaction times, fluxional dimeric species are obtained, [PtH((dpp)₂mop)]₂ (4a), [PtH((dpp)₂eop)]₂ (4b) and [PtH((dpp)₂oCy)]₂ (4c),and in the case of 4c two different isomers exist. The dihydride complexes PtH₂((dpp)₂mop) (3a), PtH₂((dpp)₂eop) (3b) and PtH₂((dpp)₂oCy) (3c), are prepared by further reaction of NaBH₄ and 2. Hydrogen cycling is facile in the dihydride complexes 3a, b, c, and oxidative addition of H₂ proceeds in a pairwise manner as determined by the observation of parahydrogen induced polarization (PHIP) in the ¹H NMR spectra. The reductive elimination of H₂ is also shown to be concerted by reaction of dihydride complexes with D₂. Crystal data: 2b (C₃₀H₃₂Cl₆OP₂Pt), monoclinic, space group P2₁/c (No. 14), a = 13.7040(1), b = 11.3430(7), c = 21.3880(9) Å, β = 97.923(9)°, V = 3292.9(2) ų and Z = 4; 2c (C₃₀H₃₀Cl₂OP₂Pt), monoclinic, space group P2₁ (No. 4), a = 11.7360(2), b = 8.4311(2), c = 14.2789(2) Å, β = 101.290(1)°, V = 1385.52(4) ų and Z = 2.     

Heterobimetallic aggregates of copper(I) with thiotungstates and thiomolybdates. Synthesis and characterization of polymeric (NEt4)3[Cu4(NCS)5WS4], (NEt4)2[(CuNCS)3WS4] and (NEt4)2[(CuNCS)4WS4], M = Mo, W

Reaction of (NEt₄)₂MS₄ (M = Mo, W) with CuCl and KSCN (or NH₄SCN) in acetone or acetonitrile affords a new set of mixed metal–sulfur compounds: infinite anionic chains Cu₄(NCS)₅MS_4³⁻ (1,2), (CuNCS)₃WS_4²⁻ (3) and two dimensional polymeric dianions (CuNCS)₄MS_4²⁻ (4,5). Crystal of 1 (M = W) and 3 are triclinic, space group P1(1:a = 10.356(2),b = 15.039(1),c = 17.356(2)Å, = 78.27(1)°, β = 88.89(2)° and γ = 88.60(1)°,Z = 2,R = 0.04 for 3915 independent data;3:a = 8.449(2),b = 14.622(4),c = 15.809(8)Å, = 61.84(3)°, β = 73.67(3)° and γ = 78.23(2)°,Z = 2,R = 0.029 for 6585 independent data). Crystals of 4 (M = W) and 5 (M = Mo) are monoclinic, space group P2₁/m,Z = 2 (4:a = 12.296(4),b = 14.794(4),c = 10.260(3)Åand β = 101.88(3)°,R = 0.034 for 4450 independent data;5:a = 12.306(2),b = 14.809(3),c = 10.257(2)Åand β = 101.99(3)°,R = 0.043 for 3078 independent data). The crystal structure determinations of 4 and 5 show that four edges of the tetrahedral MS_4²⁻ core are coordinated by copper atoms forming WS₄Cu₄ aggregates linked by eight-membered Cu(NCS)₂Cu rings. A two-dimensional network is thus formed in the diagonal (101) plane. The space between the anionic two-dimensional networks is filled with the NEt_4⁺ cations. Additional NCS groups lead to the [Cu₄(NCS)₅WS₄]³⁻ (1) trianion connected by NCS bridges forming pseudo-dimers. These latter are held together by weak CuS(NCS) interactions giving rise to infinite chains along a direction parallel to [100]. In contrast complex3 develops infinite chains from WS₄Cu₃ aggregates with the same Cu(NCS)₂Cu bridges as in 4 and 5. These chains are running along a direction parallel to [010]. The structural data of the different types of polymeric compounds containing MS_4²⁻ and CuNCS have been used to interpret vibrational spectroscopic data of the thiocyanate groups.     

Stearidonic acid (18:4ω3) in Primula florindae

Stearidonic acid (18:4ω3), which is reported to be of rare occurrence in the plant kingdom and which is of considerable dietary and pharmaceutical interest has been found in three closely related Primula species. It occurs, together with γ-linolenic acid (3–4% of the seed oil total fatty acids), in significant percentages in Primula florindae (11%), P. sikkimensis (14%) and P. alpicola (14%). 18:4(ω3 may also be of chemotaxonomic interest in the genus Primula, as high levels may be typical for section Sikkimensis. The only commercial plant source of stearidonic acid known so far is the seed oil of Ribes nigrum.     

Synthesis and structure determination of some platinum (II) complexes with hydrophilic carboxylated tertiary phosphine ligands

[Pt(COD)Cl₂] (1) reacts with PPh₂(C₆H₄COOH) (2a,b,c), PPh₂(C₆H₄COONa) (2d), PPh(C₆H₄COOH)₂ (4b,c) and P(C₆H₄COOH)₃ (6b,c) with formation of the corresponding complexes [Pt(L)₂Cl₂] (3a,b,c,d, 5b,c, 7b,c). Halide abstraction from 3a by Ag⁺ promotes coordination of the ortho-carboxylate function to platinum, yielding [ -2)}{PPh₂(C₆H₄COOH-2)}Cl] (bd8) and [ovbar|{PPh₂(C₆H₄COO-2)}₂] (bd9). Reaction of 1 with CO and 2a or 2b gives [Pt(CO)(L)Cl₂] (10a,b), wherea 1 and 2,3-bis(diphenylphosphino) maleic anhydride yields

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(bd12) and [Pt{Ph₂PC(COOH)=C(COOMe)-PPh₂}Cl₂] (13). The ¹H, ¹³C and ³¹P NMR spectra are reported and discussed. The X-ray structural analysis of 3b showed the compound to be monoclinic, space group P2₁/n, Z=4, with a=1038.5(3), B=1792.6(4), C=2311.5(4) pm, β=91.6(2)° and D_calc=1.353 g cm⁻³. The structure was solved from 4832 observed reflections with F₀ > 4 σ(F₀) and refined to a final R value of 0.0743. The Pt atom is surrounded by two Cl and two P atoms in a square planar arrangement.     

Synthesis of a series of ganglioside GM3 analogs containing a deoxy-N-acetylneuraminic acid residue.

Ganglioside GM₃ analogs containing 4-, 7-, 8-, and 9-deoxy-N-acetylneuraminic acids in the place of N-acetylneuraminic acid (Neu5Ac) have been synthesized. Glycosylation of 2-(trimethylsilyl)ethyl O-(6-O-benzoyl-β- - galactopyranosyl)-(1 → 4)-2,6-di-O-benzoyl-β- -glucopyranoside with the methyl 2-thioglycoside derivatives of the respective deoxy-N-acetylneuraminic acids, using dimethyl(methylthio)sulfonium triflate as a promoter, gave the four required 2-(trimethylsilyl)ethyl -sialosyl-(2 → 3b)-β-lactosides. These were converted via O-acetylation, selective removal of the 2-(trimethylsilyl)ethyl group, and subsequent imidate formation, into the corresponding -sialosyl-(2 → 3b)--lactose trichloroacetimidates 15, 17, 19, and 21. Glycosylation of (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol with 15, 17, 19, and 21 in the presence of boron trifluoride etherate afforded the expected β glycosides, which were transformed in good yields, via selective reduction of the azido group, coupling with octadecanoic acid, O-deacylation, and de-esterification, into the target compounds.     

The Production of γ-Decalactone by Fermentation of Castor Oil

A microbial process for the production of optically-active γ-decalactone from the ricinoleic acid present as triglycerides in castor oil has been developed, γ-decalactone (γDL) is a component of some fruit flavours, being an important organoleptic component of peach flavours. Screening showed two red yeast microorganisms, Rhodotorula glutinis and Sporobolomyces odortts to be especially suitable for this biotransformation. The process involves lipase-mediated hydrolysis of the castor oil to give free ricinoleic acid, uptake of the acid by the cells and aerobic fermentation to achieve abbreviated β-oxidation of the ricinoleic acid (12-hydroxyoleic acid) into 4-hydroxydecanoic acid (4HDA), lactonisation of the acid into γ-DL, followed by solvent extraction and distillation. γ-DL broth concentrations of 0.5-1.2g · 1^-t were obtained after 3-5 days from fermentation media containing 10 g · 1^-1 castor oil, representing an 8.3-20.0% theoretical yield. Intermediates detected were consistent with the operation of the β-oxidation pathway. Appreciable amounts of novel metabolites identified as cis and trans isomers of a tetrahydrofuran (C₁₀) were also produced. Their formation from 4HDA appeared to be non-enzymic and was favoured by anaerobic conditions. Yields of γ-DL were inversely proportional to the concentration of castor oil present in the medium, indicating that substrate inhibition takes place. The highest yields of γ-DL were obtained when castor oil was present from the beginning of the fermentation, rather than when added once the fermentation had become established, demonstrating that the β-oxidation pathway and/or transport system require continual induction. Significant amounts of γ-DL were not produced from other fatty acids, including ricinelaidic acid, the trans isomer of ricinoleic acid. γ-DL formation was dramatically inhibited by antibiotic inhibitors of oxidative phosphorylation, indicating the importance of intact β-oxidation pathways, whereas inhibitors of protein synthesis and cell-wall synthesis had much less marked effects. Selective extraction of 4HDA from the fermentation broths, and of γDL from broth lactonised by heating at low pH, could be achieved by adsorption to Amberlite XAD-1 and XAD-7 resins respectively. Some product could be recovered from the exit gases of the fermenter by passing through propylene glycol traps. This pathway is unusual in that it is a rare example of the truncated β-oxidation of a fatty acid by microorganisms. This effect probably occurs because of partial inhibition of one or more enzymes of the β-oxidation pathway by the C₁₀ hydroxylated fatty acid intermediate(s) allowing intracellular accumulation of the 4HDA, followed by leakage out of the cell; although further metabolism of this C₁₀ intermediate does take place slowly.     

Galactosylation of antibiotics using the β-galactosidase from Aspergillus oryzae

The β-galactosidase from Aspergillus oryzae has been shown to catalyze the synthesis of β-galactosides of antibiotics such as chlorphenisin and chloramphenicol using β-lactose as the galactosyl donor. Among the water-miscible organic solvents tested, 20% (v/v) acetonitrile in the reaction mixture gave the highest yield in galactoside synthesis. The products obtained were purified by preparative TLC and liquid chromatography and analyzed by ¹H-and ¹³C-NMR, and MS (FAB). Chlorphenisin and chloramphenicol were galactosylated exclusively at their primary hydroxy groups. The pH optimum for the transgalactosylation reaction was between pH 4–5. Increasing concentrations of galactosyl donor and aglycon caused increasing yields of galactosides. When the resulting galactosylated antibiotic was withdrawn from the sample, further synthesis was observed. This could be accelerated either by withdrawing the resulting monosaccharides (glucose and galactose) or exchanging them for mannose.     

Thermal and photochemical substitution reactions of CpRe(PPh3)2H2 and CpRe(PPh3)H4. Catalytic insertion of ethylene into the C-H bond of benzene

The thermal and photochemical reactions of CpRe(PPh₃)₂H₄ and CpRe(PPh₃)H₄ (Cp = η⁵-C₅H₅) with PMe₃, P(p-tolyl)₃, PMe₂Ph, DMPE, DPPE, DPPM, CO, 2,6-xylylisocyanide and ethylene have been examined. While CpRe(PPh₃)₂H₂ is thermally inert, it will undergo photochemical substitution of one or two PPh₃ ligands. With ethylene, substitution is followed by insertion of the olefin into the C-H bond of benzene, giving ethylbenzene. CpRe(PPh₃)H₄ undergoes thermal loss of PPh₃, which leads to substituted products of the type CpRe(L) H₄. Photochemically, reductive elimination of dihydrogen occurs preferentially. The complex trans-CpRe(DMPE)H₂ was structurally characterized, crystallizing in the monoclinic space group P2₁/n (No. 14) with a = 6.249(6), b = 16.671(8), c = 13.867(7) Å, β = 92.11(6)°, V = 1443.7(2.9) Å and Z = 4. The complex trans-CpRe(PMe₂Ph)₂H₂ was structurally characterized, crystallizing in the monoclinic space group P2₁/n (No. 14) with a = 7.467(3), b = 23.874(14), c = 11.798(6) Å, β = 100.16(4)°, V = 2070.2(3.4) ų and Z = 4.     

Molecular docking analysis of selected pyrimidine derivatives with human cyclin-dependent kinase 2

A series of pyrimidine were synthesized, characterized and evaluated for their antioxidant properties using the human cyclin-dependent kinase-2 protein model. Data shows that the pyrimidine derivatives (compound ID 4G) with para fluoro groups substitution at phenyl ring attached to the 4th position (IC50: 98.5µg/ml), compound 4B bearing hydroxy group at para position of phenyl ring (IC50: 117.8 µg/ml) have significant antioxidant activity. Docking data infer that compounds 4c, 4a, 4h and 4b possess binding energy (-7.9, -7.7, -7.5 and -7.4 kcal.mol-1) with 1HCK (PDB ID) receptor.