Stereoselective synthesis of (2S,3S,7S)-3,7-dimethylpentadecan-2-ol and its propionate,the sex pheromones of pine sawflies

The stereoselective synthesis of (2S,3S,7S)-3,7-dimethylpentadecan-2-ol (diprionol) and its propionate, the sex pheromones of pine sawflies (Neodiprion sp. and other), in high enantiomeric purity was achieved from (1R,3S)-2,2-dichloro-3-methylcyclopropanecarboxylic acid. The carbon skeleton of diprionol was formed via copper-catalyzed cross-coupling reactions and diastereoselective methylation of the intermediate chiral α-methylbranched aldehyde with MeTi(Oi-Pr)₃ in the presence of [(R,R)-TADDOL]Ti(Oi-Pr)₂. The latter transformation leads to a syn-adduct with high stereoselectivity, which depends on the presence and configuration of the α-stereogenic center in the aldehyde. The diastereomeric purity of (2S,3S,7S)-diprionol can be substantially increased via crystallization of its 3,5-dinitrobenzoate.     

Coordination properties of the multifunctional S,N,S zwitterionic ligand EtNHC(S)Ph2PNPPh2C(S)NEt

The reaction of trialkylphoshanes and amino-phosphanes with isothiocyanates yields adducts containing the zwitterionic thioamidyl-phosphonium P⁺C(S)N^? functional group. Ligands containing this group were not previously studied, probably due to their instability towards dissociation, in the presence of metal species able to coordinate the P atom. The ligand EtNHC(S)Ph₂PNPPh₂C(S)NEt (HEtSNS) was obtained by reaction of Ph₂PNHPPh₂ with ethylisothiocyanate and proved to be very versatile: it can be protonated giving cation H₂EtSNS⁺ and deprotonated forming the dianion–cation EtSNS^?. HEtSNS and its derivatives behave as ligands showing five possible coordination fashions, S,N,S tridentate and S,S-bidentate (with a bite-angle varying from 180° to 90°), S-monodentate, S,S bridging and N,N,N interaction. Here we describe the coordination chemistry of HEtSNS, in particular towards Rh, Cu, Ag and Au, and some properties of its complexes which are still the only examples containing the P⁺C(S)N^? zwitterionic group.     

Phase Equilibria in the Sc2S3-Ln2S3 (Ln = Dy,Er, or Tm) Systems

Phase diagrams for the Sc₂S₃-Ln₂S₃ (Ln = Dy, Er, or Tm) systems were designed in the range from 1000 K to melting temperatures. The Ln₃ScS₆ compounds that are formed in these systems crystallize in monoclinic space group P2₁/m, and melt congruently: for Dy₃ScS₆, a = 1.118 nm, b = 1.262 nm, c = 0.354 nm, β = 94.7°, 1800 K, H = 2600 MPa; for Er₃ScS₆, a = 1.113 nm, b = 1.258 nm, c = 0.353 nm, β = 94.5°, 1830 K, H = 2800 MPa; for Tm₃ScS₆, a = 1.112 nm, b = 1.229 nm, c = 0.352 nm, β = 94.3°, 1835 K, H = 2940 MPa. The LnScS₃ (Ln = Dy or Er) complex sulfides, with orthorhombic structures, space group Pnma, melt incongruently: for DyScS₃, a = 0.700 nm, b = 0.637 nm, c = 0.943 nm, 1810 K, H = 3800 MPa; and for ErScS₃, a = 0.697 nm, b = 0.633 nm, c = 0.942 nm, 1800 K, H = 3800 MPa. As the ionic radii rLn3+ and rSc3+ approach Ln Sc to each other in the row Dy-Er-Tm, the solubility in Sc₂S₃ increases, at 1670 K being equal to 13 mol % Dy₂S₃, 30 mol % Er₂S₃, and 40 mol % Tm₂S₃. LnScS₃ (Ln = Dy or Er) forms a two-sided homogeneity region, at 1670 K lying in ranges of 43–56 mol % Ln₂S₃. The eutectic temperatures and compositions are as follows: 1700 K and 66 mol % Dy₂S₃, 1730 K and 81 mol % Dy₂S₃, 1740 K and 65 mol % Er₂S₃, 1700 K and 83 mol % Er₂S₃, 1730 K and 70 mol % Tm₂S₃, and 1755 K and 84 mol % Tm₂S₃.     

Interaction in the Yb2S3-In2S3 system

A T-x diagram is designed for the Yb₂S₃-In₂S₃ system using physicochemical methods. A complex chemical reaction occurs in the system to yield ternary compounds Yb₃InS₆ (S₁), YbInS₃ (S₂), Yb₃In₅S₁₂ (S₃), and YbIn₃S₆ (S₄). In₂S₃-based limited solid solutions are found. Phases S₁, S₃, and S₄ are formed by peritectic reactions at 1260, 1200, and 1100 K, respectively. Compound S₂ melts congruently at 1390 K. Compound S₃ crystallizes in monoclinic system (a = 10.90 Å, b = 21.01 Å, c = 3.846 Å, β = 96.2°). Compounds S₁ and S₄ crystallize in orthorhombic system (for S₁, a = 16.76 Å, b = 13.70 Å, c = 3.88 Å; for S₄, a = 3.86 Å, b = 11.64 Å, c = 20.98 Å, d _exp = 4.62 g/cm³). Compound S₂ crystallizes in cubic system (a = 10.68 Å).     

Solid-state structure determination and solution-state NMR characterization of the (2R,4R)/(2S,4S)- and (2R,4S)/(2S,4R)-diastereomers of the agricultural fungicide propiconazole,the (2R,4S)/(2S,4R)-symmetrical triazole constitutional isomer,and a ditriazole analogue

Single-crystal X-ray diffraction analysis was used to determine the structure of a racemic diastereomer of the agricultural fungicide propiconazole [1-(2-(2,4-dichlorophenyl)-4-n-propyl-1,3-dioxolane-2-yl-methyl)-1-H-1,2,4-triazole] and of two by-products (a symmetrical 1,3,4-triazole racemic-constitutional isomer and a propiconazole ditriazole analogue). All three crystalline racemic-diastereomers had (2R,4S)/(2S,4R)-stereochemistry in which then-propyl group was observed in atrans-to-phenyl disposition. Propiconazole (2R,4S)/(2S,4R)-diastereomer gives crystals belonging to the monoclinic space group P2₁,/a, and, at 293 K,a=8.1192(3),b=18.9769(6),c=10.7137(4) å,Β=99.765(3)?,V=1626.8(1) å³, Z=4,R(F)=0.060, andR _w(F)=0.058. The constitutional isomer by-product (2R,4S)/(2S,4R)-1-(2-(2,4-dichlorophenyl)-4-n-pro-pyl-1,3-dioxolane-2-yl-methyl)-1-H-1,3,4-triazole gives crystals belonging to the monoclinic space group P2₁/n, and, at 293 K,a=11.1763(6),b=10.7716(4),c=14.5804(8) å,Β=107.445(4)?,V=1674.6(1) å³, Z=4,R(F)=0.043, andR _w(F)=0.043. The ditriazole byproduct (2R,4S)/(2S,4R)-1-(2-(2-chloro-4-(1,2,4-triazole-1-yl)phenyl)-4-n-propyl-1,3-dioxolane-2-yl-methyl)-1-H-1,2,4-triazole gives crystals belonging to the triclinic space groupP¯ 1, and, at 193 K,a=5.3329(8),b=8.3738(7),c=20.240(2) å, α=84.213(6)?,Β=87.20(1)?,γ=86.23(1)?,V=896.5(2) å³, Z=2,R(F)=0.046, andR _w(F)=0.051. The presence of both propiconazole (2R.4S)- and (2S,4R)-enantiomers enables the formation of a crystalline racemic modification, while the diastereomeric propiconazole (2R,4R)- and (2S,4S)-enantiomers are viscous oils. In the absence of its enantiomorphic partner, the propiconazole (2R,4S)- or (2S,4R)-enantiomers remain as viscous oils rather than form chiral crystals.     

Stereoselective synthesis,solution structure and metal complexes of (1S,2S)-2-amino-1-hydroxyalkylphosphonic acids

The highly stereoselective synthesis of (1S,2S)-2-amino-1-hydroxyalkylphosphonic acids was achieved by addition of dimethyl phosphite to N-protected aminoaldehydes. Relative configuration and solution conformations of (1S,2S)-2-amino-1-hydroxy-alkylphosphonic acids (in D₂O) and their dimethyl esters (in CDCl₃ and CD₃OD) were established by means of NMR basing on the dependence between observed values of coupling constants (³J_HH, ³J_PC, ³J_HP) and corresponding dihedral angles. Potentiometric and spectroscopic methods were used for the evaluation of the structure of the complexes of (1S,2S)-2-amino-1-hydroxy-alkylphosphonic acids with Zn(II) and Cu(II) ions in aqueous solutions.     

Expedient asymmetric synthesis of (2S,3S)-Boc-phenylalanine epoxide,a key intermediate for the synthesis of biologically active compounds

The asymmetric synthesis of (2S,3S)-3-(tert-butoxycarbonyl)amino-1,2-epoxy-4-phenylbutane [(2S,3S)-Boc-phenylalanine epoxide] has been achieved in six steps and in 55% overall yield from the N-benzylimine derived from (R)-2,3-O-isopropylidene-glyceraldehyde. The required vic-aminodiol intermediate was obtained through a highly diastereoselective addition of benzylmagnesium chloride to the N-benzylimine in the presence of BF₃·OEt₂ as an imine precomplexing agent.     

Chemoenzymatic synthesis of (3R,4S)- and (3S,4R)-3-methoxy-4-methylaminopyrrolidine

An efficient and a convenient enantioselective synthesis of (3R,4S)-3-methoxy-4-methylaminopyrrolidine has been carried out by a lipase-mediated resolution protocol. This method describes the preparation of (±)-1-Cbz-cis-3-azido-4-hydroxypyrrolidine starting from commercially available diallylamine followed by ring-closing metathesis (RCM) via S_N2 displacement reactions. Pseudomonas cepacia lipase immobilized on diatomaceous earth (Amano PS-D) provides (3R,4S)-11 and (3S,4R)-12 in an excellent enantiomeric excess.     

A flexible and modular stereoselective synthesis of (9R,10S)-dihydrosterculic acid

(9R,10S)-Dihydrosterculic acid has been prepared from (S_S,S_S)-1,1-bis(p-tolylsulfinyl)methane in a sequence involving an asymmetric Corey–Chaykovsky cyclopropanation and two sulfoxide/lithium exchange reactions. In most steps, the reaction conditions had to be optimized for the unbranched alkyl substituents, which were prone to Evans–Mislow rearrangements and subsequent degradation.     

Efficient stereospecific synthesis of (S,S)-3-methoxy-4-methylaminopyrrolidine

Efficient stereospecific synthesis of (S,S)-3-methoxy-4-methylaminopyrrolidine, an important intermediate for a novel quinolone antitumor agent AG-7352 is presented. Starting from either d- or l-tartaric acid, a stereospecific synthesis of the chiral pyrrolidine was achieved via two S_N2 displacement reactions. From the results of this synthetic study, the absolute structure of AG-7352 was chemically determined.     

Asymmetric hydrogenation of α,β-unsaturated ketones catalyzed by Ru–TPPTS–(S,S)-DPENDS complex in ionic liquids

The asymmetric hydrogenation of α,β-unsaturated ketones catalyzed by the achiral ruthenium monophosphine complex RuCl₂(TPPTS)₂ [TPPTS: P(m-C₆H₄SO₃Na)₃] modified by (S,S)-DPENDS [disodium salt of sulfonated (S,S)-1,2-diphenyl-1,2-ethylene-diamine] was investigated in ionic liquid [RMIM]Ts (1-alkyl-3-methylimidazolium p-methylphenylsulfonates, R = ethyl, butyl, octyl, dodecyl). Chemoselectivity of 100% and 75.9% ee were obtained for benzalacetone under the optimized conditions. The resulting products can be easily separated from the catalyst immobilized in ionic liquid [EMIM]Ts by extraction with n-hexane, while the catalyst can be reused seven times without the loss of catalytic activity and enantioselectivity. Especially, the addition of water can improve the performance of the catalyst.     

Stereospecific ligands and their complexes. IV: Synthesis,characterization and cytotoxicity of novel platinum(IV) complexes with ethylenediamine-N,N′-di-S,S-2-propanoate and halogenido ligands: Crystal structure of s-cis-[Pt(S,S-eddp)Cl2]·4H2O and uns-cis-[Pt(S,S-eddp)Br2]

The syntheses of two novel platinum(IV) complexes of formula [PtX₂(S,S-eddp)]·nH₂O (S,S-eddp = ethylenediamine-N,N′-di-S,S-2-propanoate ion, X = chlorido (1) or bromido (2), n = 4, 0) are reported. The complexes have been obtained by direct reaction of corresponding potassium hexahalogenidoplatinate(IV) with neutralized ethylenediamine-N,N′-di-S,S-2-propanoic acid (H₂-S,S-eddp). The complexes were characterized by elemental analysis, infrared, ¹H and ¹³C NMR spectroscopy. The spectroscopically predicted geometrical configurations of the obtained complexes were confirmed by X-ray analyses of the crystal structures of the s-cis-[Pt(S,S-eddp)Cl₂]·4H₂O and uns-cis-[Pt(S,S-eddp)Br₂]. These complexes displayed significantly lower in vitro cytotoxicity in comparison to cisplatin.     

Efficient enantioselective synthesis of (2R,3R)- and (2S,3S)-3-hydroxyleucines and their diastereomers through dynamic kinetic resolution

(2R,3R)- and (2S,3S)-3-Hydroxyleucines, components of cyclodepsipeptides, papuamides and polyoxypeptins, were efficiently synthesized along with their diastereomers from the corresponding β-keto-α-amino acid ester through dynamic kinetic resolution using RuCl₂(binap)-catalyzed hydrogenation.     

Crystal structure of 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo [8.8.8]hexacosane (2S,3S)-tartrate

Crystal structure of (2S,3S)-tartrate of 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo-[8.8.8]hexacosane, [H₂(Crypt-222)]²⁺·(C₄H₄O₆)^2? (I) has been studied by single crystal X-ray diffraction. Triclinic structure of I (space group P1, a = 8.424 Å, b = 13.011 Å, c = 13.806 Å; α = 116.37°, β = 106.45°, γ = 91.81°; Z = 2) was solved by the direct method and refined in the full-matrix anisotropic approximation to R = 0.140 for 5850 measured independent reflections (automated diffractometer CAD-4, λMoK _α). In the structure of I, two independent dications of 2.2.2-cryptand (nitrogen atoms are protonated) are linked to the approximate inversion symmetry and have a rare conformation of exo-exo type, when two atoms sitting on N atoms are protruded out of their cavity. The centroids of two crystallographically unique (2S,3S)-tartrate dianions are bound with the same approximate inversion center. An extended system of hydrogen bonds is developed in the crystal of I.     

Detailed electron spectrometric study of the ionization of H2 by He* (21 S, 23 S)

The energy spectra of electrons released in thermal energy (≈ 50 meV) ionizing collisions of He*(2¹ S, 2³ S) with H₂ have been measured with high resolution and low background. Based on a detailed data analysis, we report accurate H ₂ ⁺ (v′) vibrational populationsP(v′) for both He*(2¹ S)+H₂(v′=0–10) and He*(2³ S)+H₂(v′=0–15) and the spectral shapeS(ε) for the individual vibrational peaks. The vibrational populationsP(v′) are quite similar to the Franck-Condon factorsf _v ′0 for unperturbed H₂(v″=0)→H ₂ ⁺ (v′) transitions, but, more in detail, the ratiosP(v′)/f _v ′0 show a characteristically differentv′-dependence for He*(2³ S), He*(2¹ S), and HeI_α(58.4 nm) ionization. The vibrational level separations in the He*(2¹ S, 2³ S)+H₂ spectra agree with those in the HeI photoelectron spectrum to within 1–2 meV. The spectral shapesS(ε) are characteristically different for He*(2¹ S)+H₂ and He*(2³ S)+H₂, reflecting the respective differences in the entrance channel potentials, as determined previously in ab initio calculations and from scattering experiments.     

Studies towards the synthesis of (1R,2S)- and (1S,2S)-1,2-epoxy-3-hydroxypropylphosphonates and (1S,2S)- and (1R,2S)-2,3-epoxy-1-hydroxypropylphosphonates

The trans-configured fosfomycin analogue, diethyl (1S,2S)-1,2-epoxy-3-hydroxypropylphosphonate, was synthesised by the intramolecular Williamson reaction of diethyl (1S,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate. The cis-analogue was obtained as O-ethyl or O,O-diethyl (1R,2S)-1,2-epoxy-3-hydroxypropylphosphonates, when (1R,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate or its 3-O-trityl derivative were used as starting materials, respectively. The intramolecular Williamson cyclisations of diethyl (1S,2R)- and (1R,2S)-1-benzyloxy-3-hydroxy-2-mesyloxypropylphosphonates led to diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, respectively, with the concomitant formation of diethyl (E)-1-benzyloxy-3-hydroxyprop-1-en-1-phosphonate. From diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, enantiomerically pure diethyl (1S,2S)- and (1R,2S)-1,2-dihydroxypropylphosphonates were obtained by catalytic hydrogenation, while diethyl (1S,2S)- and (1R,2S)-3-acetamido-1,2-dihydroxypropylphosphonates were produced after epoxide ring opening with dibenzylamine, acetylation and hydrogenolysis.     

Total synthesis of (4R,5S,6E,14S)- and (4R,5S,6E,14R)-cystothiazoles F

Total synthesis of (4R,5S,6E,14S)- and (4R,5S,6E,14R)-cystothiazoles F 3 was achieved from the chiral bithiazole-type primary alcohols [(S)- and (R)-4-ethoxycarbonyl-2′-(1-hydroxymethylethyl)-2,4′-bithiazoles 8], which were obtained based on the enzymatic resolution of racemic alcohol 8 and its acetate 9. From a direct comparison by means of chiral HPLC between natural cystothiazole F 3 and synthetic compounds [(4R,5S,6E,14S)- and (4R,5S,6E,14R)-cystothiazoles 3], natural cystothiazole F 3 was found to be a 33:67 diastereomeric mixture [(4R,5S,6E,14S)-3:(4R,5S,6E,14R)-3 = 33:67].     

Synthesis of methyl (E)-2-[(3S,4S)-4-hydroxy-3-(pent-3-yloxy)-pyrrolidin-2-ylidene]propanoate and its unusual recyclization

Methyl (2E,4S,5S)-5-hydroxy-6-mesyloxy-2-methyl-4-(pent-3-yloxy)hex-2-enoate was synthesized from l-tartaric acid. Attempted substitution of the mesyloxy group by the reaction with NaN₃ directly led to methyl (E)-2-[(3S,4S)-4-hydroxy-3-(pent-3-yloxy)pyrrolidin-2-ylidene]propanoate. The latter on treatment with CF₃COOH and then NaOH gave methyl (2E)-2-methyl-4-[(S)-oxiran-2-yl]-4-(pent-3-yloxy)but-2-enoate.     

Convenient access to sterically hindered C2 chiral 2,2,5,5-tetraphenyltetrahydrofuran-3,4-diols: intramolecular selective 1,4-cyclocondensation of (2R,3R)- and (2S,3S)-1,1,4,4-tetraphenylbutanetetraols

Sterically hindered C₂ chiral (3R,4R)- and (3S,4S)-2,2,5,5-tetraphenyltetrahydrofuran-3,4-diols have been conveniently prepared in a very high yield via heterogeneous intramolecular selective 1,4-cyclocondensation of (2R,3R)- and (2S,3S)-1,1,4,4-tetraphenylbutanetetraol in concentrated hydrohalic acids, respectively. Preliminary examination of additives for the Barbas–List reaction showed that in certain cases, the hindered C₂ chiral tetrahydrofuran-3,4-diols were better chiral auxiliaries than enantiopure (R)- and (S)-1,1′-bi-2-naphthols.     

Molekulare Zusammensetzung von flüssigem Schwefel. Teil 2: Qualitative Analyse und Isolierung von S7, S12, α-S18 und S20

Molecular Composition of Liquid Sulfur. Part 2: Qualitative Analysis and Preparation of S₇, S₁₂, α-S₁₈, and S₂₀ from S₈ Raman spectra of sulfur melts (115–300°C), of quenched melts and of CS₂ extracts of quenched melts show besides S₈ the presence of S₆ and S₇. Formation of S₇ from S₈ at 120°C takes more than 8 h; the S₇ equilibrium concentration increases with temperature. Pure crystalline S₇, S₁₂, α-S₁₈ and S₂₀ are prepared on a preparative scale by fractional extraction, crystallization, flotation and precipitation of quenched sulfur melts. Also a mixture of larger rings (S_x; x? = 25) has been isolated. Infrared and Raman spectra of α-S₁₈, S₂₀ and S_x are reported.