Enantioselective synthesis of (2R,3R)- and (2S,3S)-β-hydroxyornithine

An efficient and short synthesis of (2R,3R)- and (2S,3S)-β-hydroxyornithine 1a-b is described using Sharpless asymmetric dihydroxylation and regioselective nucleophilic opening of a cyclic sulfite as the key steps.     

Reagent-controlled diastereoselective synthesis of (2S,3R)- and (2R,3R)-2,3-diaminobutanoic acid derivatives using proline-catalyzed α-hydrazination reaction

(2S,3R)- and (2R,3R)-2,3-Diaminobutanoic acid (Dab) derivatives were efficiently synthesized from Cbz-(R)-alanine using the proline-catalyzed diastereoselective α-hydrazination reaction and the SmI₂-promoted reductive cleavage of the N-N bond as the key steps.     

The efficient synthesis of (3R,4R,5R)-3-amino-4,5-dimethyl-octanoic acid, a chiral β-amino acid with potent affinity for the α2δ protein

A chiral β-amino acid containing three contiguous chiral centers was synthesized efficiently in 11 steps, employing enantio-enriched β-ketoester as a key intermediate, via stereoselective catalytic hydrogenation of the corresponding enamide. Stereoselective 1,4-addition of a methyl group and protonation were key to the preparation of the desired acid 12. Mild and efficient reaction conditions were applied to the enamine formation and protection to avoid epimerization at C-4 of compounds 13 and 14. The final compound was found to display potent affinity for the α₂δ-protein that is a recognized drug target for the treatment of a variety of diseases.     

The systems Zr(Nb,Ti)(R)O2−δ, R=Yb, Ca—optimization of mixed conductivity and comparison with results of other systems (R=Y and Gd)

In this work we address the optimization of mixed conductivity in fluorite compounds based on zirconia. Phase relations of the new systems YbO_1.5-NbO_2.5-ZrO₂, and CaO-NbO_2.5-ZrO₂ are presented. The limit of the cubic defect fluorite phase in YbO_1.5-NbO_2.5-ZrO₂ closely resembles that of the system YO_1.5-NbO_2.5-ZrO₂, whilst in CaO-NbO_2.5-ZrO₂ is narrow extending to include composition Ca_0.255Nb_0.15Zr_0.595O_1.82 at 1500°C. The influence of dopant ion size, charge and composition on ionic conduction is assessed and parallels are drawn with the systems YO_1.5-NbO_2.5-ZrO₂ and YO_1.5-TiO₂-ZrO₂. Comparison of these results with published data on the Ti containing systems CaO-TiO₂-ZrO₂, GdO_1.5-TiO₂-ZrO₂ shows that the highest mixed conducting compositions can only be offered in the system YO_1.5-TiO₂-ZrO₂ out of all the systems here studied.     

The first asymmetric total synthesis of (R)-tuberolactone, (S)-jasmine lactone and (R)-δ-decalactone

A general synthetic approach has been developed for the first asymmetric total synthesis of tuberolactone 1, jasmine lactone 2 and δ-decalactone 3. The key step is the selective hydrogenation of triple and endocyclic double bonds in the key intermediate 4.     

Host compounds (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) and (2R,3R)-(−)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT) with guests o-, m- and p- toluidine: A comparative investigation

In this work, we have compared the host abilities of closely related compounds (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) and (2R,3R)-(?)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT) when these were recrystallized from single and mixed toluidine guests. Significant differences in host behaviour and selectivities were revealed and these were explained by means of single crystal diffraction experiments. Thermal analyses were used to determine the relative complex stabilities, and these data correlated exactly with the host selectivity orders for both TETROL and DMT.     

d- and l-Serine, useful synthons for the synthesis of 24-hydroxyvitamin D3 metabolites. A formal synthesis of 1α,24R,25-(OH)3-D3, 24R,25-(OH)2-D3 and 24S,25-(OH)2-D3

d- and l-Serine have been used for the enantioselective synthesis of tosylates 7a and 7b, useful building blocks for the synthesis of triols 5a and 5b which have already been obtained via a diastereoselective synthesis and used for the synthesis of 2a, 2b and 2c. We have thus performed a formal synthesis of 24S,25-(OH)₂-D₃, 24R,25-(OH)₂-D₃ and 1α,24R,25-(OH)₃-D₃.     

Synthesis of β-chloro α-amino acids: (2S,3R)- and (2S,3S)-3-chloroleucine

The first syntheses of (2S,3R)- and (2S,3S)-3-chloroleucine (3-chloro-d-leucines 1 and 2) have been achieved from d-3-hydroxyleucine and allo-d-3-hydroxyleucine, respectively, through the formation of the corresponding N-Cbz β-lactones, followed by a ring opening promoted by lithium chloride and a debenzylation process.     

The first stereoselective total synthesis of (3S,4R)-dihydroxy-(6S)-undecyl-α-pyranone and total synthesis of (2S,3R,5S)-(−)-2,3-dihydroxytetradecan-5-olide

The first total synthesis of (3S,4R)-dihydroxy-(6S)-undecyl-α-pyranone 1 and total synthesis of (2S,3R,5S)-(−)-2,3-dihydroxytetradecan-5-olide 2 have been achieved in five steps in a highly stereoselective manner using Maruoka allylation, olefin cross-metathesis, and Sharpless asymmetric dihydroxylation as key steps.     

Interplay between Cu and Fe Valences in BaR(Cu0.5Fe0.5)2O5+δ Double Perovskites with R=Lu, Yb, Y, Eu, Sm, Nd, and Pr

We have conducted a systematic ⁵⁷Fe Mössbauer study on BaR(Cu_0.5Fe_0.5)₂O_5+δ double perovskites with various oxygen contents and rare-earth elements (R=Lu, Yb, Y, Eu, Sm, Nd, and Pr). In samples based on R=Lu, Yb, Y, Eu, Sm the oxygen content remained at δ≈0, upon reductive or oxidative heat treatments under normal pressure. The larger rare-earth elements, i.e. Nd or Pr, readily allowed for continuous oxygen content tuning up to δ≈0.3. By employing high-pressure heat treatments higher oxygen contents were achieved for all samples. The Néel temperature of the samples was found to decrease with increasing amounts of oxygen entering the lattice. In high-pressure oxygenated samples the decrease was less severe indicating that despite the incorporation of oxygen a large amount of Fe still remains in the high-spin trivalent state. By using charge-neutrality arguments together with the relative intensities of the Mössbauer spectral components the average valences of Fe and Cu were obtained. Oxygenation under normal pressure led to a corresponding increase of the valence of Fe, while Cu remained divalent. Upon high-pressure heat treatment equal amounts of Fe³⁺ and Cu²⁺ were found to be oxidized to Fe⁵⁺ and Cu³⁺, respectively.     

Synthesis of dipyrrolo[2,3-a:1′,2′,3′-fg]acridin-12(1H)-ones

Acylation reactions of 4,6-dimethoxyindoles with glyoxyloyl chlorides were achieved by the use of graphite powder in 1,2-dichloroethane at reflux. The products were monoketones as a result of decarbonylation, rather than the expected 1,2-diketones. Treatment of these monoketones with base led to their cyclisation and elimination of methanol to afford the novel dipyrrolo[2.3-a:1′,2′,3′-fg]acridin-12(1H)-ones.     

Synthesis of (3R,4S,5S,9S)-3,5,9-trihydroxy-4-methylundecanoic acid δ-lactone

Radical-mediated opening of a chiral trisubstituted epoxy alcohol using cp₂TiCl furnished the ‘2-methyl-1,3-diol’ moiety with the desired stereochemistry, which led to a total synthesis of (3R,4S,5S,9S)-3,5,9-trihydroxy-4-methylundecanoic acid δ-lactone 1.     

Stereoselective synthesis of (22Z)-25-hydroxyvitamin D2 and (22Z)-1α,25-dihydroxyvitamin D2

Two new vitamin D₂ analogues, (22Z)-25-(OH)-D₂ and (22Z)-1α,25-(OH)₂-D₂, were serendipitously synthesized from vitamin D₂ and using the Julia-Kocienski olefination.     

Synthesis and reactivity towards carbon monoxide of an optically active endo five-membered ortho-cyclopalladated imine: X-ray molecular structure of trans-(μ-Cl)2[Pd(κ-C,N-(R)-C6H4-CHN-CHMe-Ph)]2

(R)-1-Phenylethyl-benzylidene-amine (1) reacted with Pd(OAc)₂ in acetic acid at 60 °C under nitrogen affording the acetato-bridged dinuclear endo five-membered ortho-cyclopalladated compound (μ-OAc)₂[Pd(κ²-C,N-(R)-C₆H₄-CHN-CHMe-Ph)]₂ (2) in 65% yield. Compound 2 was converted by a metathesis reaction with LiCl into the corresponding chloro-bridged dinuclear cyclopalladated compound (μ-Cl)₂[Pd(κ²-C,N-(R)-C₆H₄-CHN-CHMe-Ph)]₂ (3). ¹H NMR of CDCl₃ solutions of compounds 2 and 3 treated separately with py-d₅, (R)-1-phenylethylamine and racemic 1-phenylethylamine were consistent with the endo cyclopalladated structure and the R absolute configuration of the chiral carbon atoms of compounds 2 and 3. Compounds 2 and 3 reacted with carbon monoxide in methanol affording, as major compounds, methyl 2-formylbenzoate (91% chemical yield) and the epimers of 3-methoxy-2-[(R)-1-phenylethyl]isoindolin-1-one (64% chemical yield) in ca. 20% diastereomeric excess, respectively. The trans isomer of compound 3 crystallized in the P2₁ monoclinic space group with a = 10.430(4) Å, b = 12.082(8) Å, c = 11.168(4) Å and β = 95.20(3)° and presented C-H?Cl intramolecular and C-H?Pd intermolecular non-conventional hydrogen bonds.     

Synthesis and structures of Cs4[(UO2)2(C2O4)(SO4)2(NCS)2] · 4H2O and (NH4)4[(UO2)2(C2O4)(SO4)2(NCS)2] · 6H2O

Single crystals of Cs₄[(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂] · 4H₂O (I) and (NH₄)₄[(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂] · 6H₂O (II) have been synthesized and studied by X-ray diffraction. The crystals of both compounds are orthorhombic with the space group Pbam, Z = 2, and unit cell parameters a = 12.0177(3) ?, b = 18.6182(5) ?, c = 6.7573(10) ?, R = 0.0376 (I); a = 11.6539(9) ?, b = 18.3791(13) ?, c = 6.7216(5) ?, R = 0.0179 (II). The main structural units of crystals I and II are [(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂]⁴⁻ chains belonging to the crystal-chemical group A₂K⁰²B₂²M₂¹ (A = UO₂²⁺, K⁰² = C₂O₄²⁻, B² = SO₄²⁻, M¹ = NCS⁻) of the uranyl complexes. The uranium-containing chains are joined into a three-dimensional framework due to a system of electrostatic interactions with the cesium or ammonium ions in the structure of I. In the structure of II, this framework is additionally stabilized by hydrogen bonds involving the outer-sphere water molecules and ammonium ions. Original Russian Text ? I.V. Medrish, A.V. Virovets, E.V. Peresypkina, L.B. Serezhkina, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 7, pp. 1115–1120.     

A practical synthesis of the PPARα agonist, (R)-K-13675, starting from (S)-2-hydroxybutyrolactone

A practical synthesis of optically pure PPARα agonist, (R)-K-13675, is described. This process is based on the use of (S)-2-hydroxybutyrolactone, which can be transformed into the requisite n-butyl (S)-2-hydroxybutanoate in an efficient manner. A key reaction is the etherification between the phenol and n-butyl (S)-2-trifluoromethanesulfonyloxybutanoate to give the phenyl ether in excellent yield without loss of optical purity.     

Functionalised tetraarylstannanes Sn[C6H4-R]4 (R=-CH(CH2O)2, -CHO, -COOH, -CHN-NH-C6H3-2,4-(NO2)2, -CH2OH, -CO-NH-CH2-COO-CH3, -CH[N(C2H4)2O]2)

Reaction of tin tetrachloride with the appropriate Grignard reagent gave Sn[C₆H₄-CH(OCH₂)₂]₄ (2), which was transformed to Sn[C₆H₄-CHO]₄ (3) and its hydrazido and amino derivatives Sn[C₆H₄-CHN-NH-C₆H₃-2,4-(NO₂)₂]₄ (5) and Sn{C₆H₄-CH[N(C₂H₄)₂O]₂}₄ (8). Oxidation of (3) produced Sn[C₆H₄-COOH]₄ (4) while reduction of (3) gave Sn[C₆H₄-CH₂-OH]₄ (6). From the acid 4, an amino acid Sn[C₆H₄-CO-NH-CH₂-CO-OCH₃]₄ (7) could be obtained by reaction with the methyl ester of glycine. All compounds were isolated in pure form with yields of 40-64% and were characterised by spectroscopic means (heteronuclear NMR) or by X-ray structure determination (3).     

SO2, HCl, CO2, HS und S?urechloride

Ohne Zusammenfassung     

Enantioselective epoxidation of α,β-enones promoted by (1R,3S,4S)-2-azanorbornyl-3-methanol as an organocatalyst

(1R,3S,4S)-2-Azanorbornyl-3-methanol was synthesized form (R)-1-phenylethylamine and used as a catalyst for the enantioselective epoxidation of α,β-enones to afford the corresponding epoxides in good yields and high enantioselectivities at room temperature.     

α- to β-[C6H4(NH3)2]2Bi2I10 reversible solid-state transition, thermochromic and optical studies in the p-phenylenediamine-based iodobismuthate(III) material

α-[C₆H₄(NH₃)₂]₂Bi₂I₁₀, which is a new material containing low-dimensional iodobismuthate anions, was synthesized and through its single crystal X-ray diffraction measurements, was proven to crystallize at room temperature in the centrosymmetric space group P2₁/c. It consists of a p-phenylenediammonium dication and a discrete (0-D) anion built up of edge-sharing bioctahedron. Due to the hydrogen bonds and the interatomic distances (Bi-I, I?I and π-π) changes, α-phase was transformed into the corresponding centrosymmetric β-phase, β-[C₆H₄(NH₃)₂]₂Bi₂I₁₀, through a single-crystal to single-crystal transformation occurring upon cooling to −28/−26 °C. Below the transition temperature, β-[C₆H₄(NH₃)₂]₂Bi₂I₁₀ crystallizes in the monoclinic system, centrosymmetric space group P2₁/n. Besides, the optical transmission measurements on α-[C₆H₄(NH₃)₂]₂Bi₂I₁₀ thin films have revealed two absorption bands at 2.47 and 3.01 eV. Finally, two room temperature photoluminescence emissions attributed to excitons radiative recombinations confined within the bioctahedra Bi₂I₁₀⁴⁻, were observed in the red spectral range at 1.9 and 2.05 eV energy.