Asymmetric synthesis of (S)-homocitric acid lactone

Starting from (S)-phenylalanine, an asymmetric synthesis of (S)-homocitric acid lactone was achieved using Seebach’s SRS methodology. An intermediate for the synthesis of the (S)-per-homocitric acid lactone has also been synthesized.     

Enantioselective synthesis of (R)-homocitric acid lactone

An expedient enantioselective approach to (R)-homocitric acid lactone from an ephedrine-derived morpholine-dione, a cationic glycolate equivalent, is described.     

Biphenyl quinolizidine lactone alkaloids from “sinicuichi” (Heimia salicifolia)

Six new biphenyl quinolizidine lactone alkaloids: 14α-hydroxydecodine (1), 14β-hydroxydecodine (2), 4″-O-demethylheimidine (3), 4″-O-demethyl-9β-hydroxyvertine (4), 4″-O-demethylvertine N-oxide (5), and 4″-O-demethyl-9β-hydroxyvertine N-oxide (6) were isolated from so-called “sinicuichi” (origin: Heimia salicifolia) together with 18 known alkaloids. Their structures were determined by spectroscopic analyses and chemical conversions.     

The facile synthesis of a large ring lactone by acid-catalysed cyclisation of an (z)-ene-diyne hydroxy acid precursor.

A Large ring lactone is obtained in good yield by acid catalysed cyclisation of the w-hydroxy acid precursor.     

Asymmetric synthesis of (+)-(S)-Massoia lactone, pheromone of Idea leuconoe. Formal total synthesis of valilactone and lachnelluloic acid

Simple and efficient asymmetric synthesis was developed of the cyclic scaffold of (-)-valilactone, an effective inhibitor of the pancreas lipase, applying the Keck allylation in the key stage of building up the carbon skeleton of the target molecule and of the unnatural (S)-isomer of Massoia lactone, lachnelluloic acid, possessing fungicidal properties, and (5R,7S)-7-hydroxy-5-dodecanolid, pheromone component of the Large Tree Nymph butterfly Idea leuconoe.     

Preparation of new amide-linked pseudodisaccharides by the carboxymethylglycoside lactone (CMGL) strategy

6-Aminodeoxy sugars react with carboxymethyl 3,4,6-tri-O-acetyl-α-d-glucopyranoside 2-O-lactone (α-CMGL) to provide the corresponding new amide-linked glucose/glucose or glucose/galactose pseudodisaccharides in good yields. The strategy is extended to the synthesis of an amide-linked sugar/nucleoside adduct.     

Concise synthesis of enantiopure erythro-saccharinic acid lactone and potassium (2R,3R)-2,3,4-trihydroxy-2-methylbutanoate

A short and efficient approach was applied to the total synthesis of erythro-saccharinic acid lactone and the leaf-closing substance potassium (2R,3R)-2,3,4-trihydroxy-2-methylbutanoate from a 2-C-hydroxymethyl-d-erythrose derivative, using a combined strategy.     

Stereoselective total synthesis of polyketide lactone, (3R,4S,5S,9S)-3,5,9-trihydroxy-4-methylundecanoic acid δ-lactone

The total synthesis of lactone 1 has been described. The convergent asymmetric synthesis relies on the use of an Evans’ syn-aldol, chain extension with lithio tert-butyl acetate, and the stereoselective reduction of a ketone as the key reactions.     

Synthesis of enantiomerically pure (3R,4R,5R)-4-hydroxy isoleucine lactone

A short four-step synthesis of (3R,4R,5R)-4-hydroxyisoleucine lactone with total control of stereochemistry is reported, the key intermediate being the didehydroamino acid derivative arising from an aldol dehydration reaction between a glycine anion equivalent and butan-2,3-dione.     

Molecular and vibrational structure of the extracellular bacterial signal compound N-butyryl-homoserine lactone (C4-HSL)

The molecular and vibrational structure of the title compound (C4-HSL) was studied by experimental and theoretical methods. The infrared (IR) absorption spectrum was measured in the solid state and in CCl₄ suspension. The observed absorption bands were compared with transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT) calculations. Two stable molecular conformations were predicted, corresponding to an endo- and an exo-conformer with similar energies. Intermolecular amide–amide hydrogen bonding in the crystal state was approximated by a simple cluster model, leading to excellent agreement with the observed solid state IR spectrum. Due to the low solubility of C4-HSL in common solvents for IR spectroscopy, such as CS₂ and CCl₄, a liquid solution spectrum of pure, monomeric C4-HSL was not obtained. However, absorbance peaks observed in oversaturated CCl₄ solution could be assigned to distinct contributions from suspended micro-crystalline aggregates and dissolved monomeric species. The key vibrational bands of the monomeric form of C4-HSL are reported here for the first time: 3425 cm^?1 [ν(N–H)], 1784 cm^?1 [ν(CO), lactone], 1688 cm^?1 [amide I], and 1494 cm^?1 [amide II] (CCl₄).     

Comparative coordination ability of N-(2-hydroxyethyl)aminoacetic acid and O-(2-hydroxyethyl)hydroxyacetic acid in the copper(II) complexes

Copper(II) complexes based on N-(2-hydroxyethyl)aminoacetic and O-(2-hydroxyethyl)hydroxyacetic acids were synthesized. Their structures were studied by X-ray diffraction analysis. The coordination spheres of the copper metal center were compared in the condensed phase for the both ligands.     

Multienzymatic preparation of 3-[(1R)-1-hydroxyethyl]benzoic acid and (2S)-hydroxy(phenyl)ethanoic acid

The use of two oxidoreductases (an aldoketo reductase from Escherichia coli JM109 and an alcohol dehydrogenase from Lactobacillus brevis) has demonstrated that it is possible to prepare enatiomerically pure diols in a one-pot operation. The reactions were applied to the synthesis of (1R)-1-[3-(hydroxymethyl)phenyl]ethanol and (1S)-1-phenylethane-1,2-diol, using a two-step procedure. The yield is nearly quantitative and the enantiomeric purity is greater than 95%. A third step has been introduced by adding a cell biocatalyst showing dihydrodiol dehydrogenase activity from Pseudomonas fluorescens N3. This allows for the preparation of 3-[(1R)-1-hydroxyethyl]benzoic acid and (2S)-hydroxy(phenyl)ethanoic acid.     

Stereoselective synthesis of a new trihydroxyindolizidine lactone

A general approach to 1,6,7-trihydroxyindolizidin-8-carboxylates is illustrated through the synthesis of a γ-lactone in an enantiopure form in seven steps starting from (3S)-3-t-butyloxy-1-pyrroline N-oxide and the acetonide of (2E,4S)-4,5-dihydroxy-2-pentenoic acid derived from (S)-malic acid and mannitol, respectively. The process was completely stereoselective and allowed the total control of the relative and absolute configuration of the five contiguous stereocentres of the product.     

Synthesis of anti-Alzheimer (R)-arundic acid

The asymmetric synthesis of the anti-Alzheimer agent (R)-arundic acid has been performed via a diastereoselective photodeconjugation reaction as the key-step. The synthetic approach involves a readily available chiral auxiliary, diacetone-d-glucose, and allows access to either enantiomer as illustrated by the synthesis of (S)-arundic acid. Both enantiomers were obtained in 88% ee using the same chiral auxiliary.     

Structure and thermal reactivity of Zn(II) salts of isocinchomeronic acid (2,5-pyridinedicarboxylic acid)

The synthesis, an improved refined crystal and molecular structure re-determination, and the thermal decomposition behavior of two Zn(II) derivatives of isocinchomeronic acid (2,5-pyridinedicarboxylic acid or H₂2,5-pydc) are presented. [Zn(2,5-pydc)(H₂O)₃Zn(2,5-pydc)(H₂O)₂]₂ (1) crystallizes in the triclinic P-1 space group with a = 7.106(2), b = 11.450(2), c = 11.869(1) Å, α = 107.29(1), β = 104.08(1), γ = 90.32(2)°, and Z = 2. [Zn(2,5-pydc)(H₂O)₂] · H₂O (2) is orthorhombic (P2₁2₁2₁ space group), with a = 7.342(1), b = 9.430(1), c = 13.834(2) Å, and Z = 4. The structures were refined to agreement R ₁-factors of 0.0315 (1) and 0.0336 (2). Complex (1) is arranged as molecular Zn₄(2,5-pydc)₄(H₂O)₁₀ tetramers, the cages of which define channels that remain unblocked by anions. Compound (2) is polymeric with Zn(2,5-pydc)(H₂O)₂ and Zn(2,5-pydc)(H₂O)₃ units linked through bridging ligands. Both compounds were synthesized under mild conditions in aqueous media, without need to resort to hydrothermal media. Changing the pH from 4.51 to 5.75 suffices to direct the chemical processes toward the orthorhombic compound rather than to the triclinic one.     

Synthesis and structures of cooligo(lactone) macromonomers

Cooligo(lactone) macromonomers were prepared by cooligomerisation of (S,S)-3,6-dimethyl-1,4-dioxane-2,5-dione (L-lactide), 1-oxacyclohexane-2-one (δ-valerolactone) or 1-oxacycloheptane-2-one (ε-caprolactone), initiated by 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]-propane (BisGMA). Two different reaction ways were used for the synthesis: parallel reaction and step reaction of lactones and L-lactide. The macromonomers were characterised by differential scanning calorimetry (DSC), size exclusion chromatography (SEC), ¹H- and ¹³C-NMR spectroscopy and MALDI-TOF mass spectrometry. Cooligo(lactone) macromonomers prepared by parallel and by step reaction show different molecular structures resulting in different properties. Their glass transition temperatures depend on the molar ratio of lactide and lactone as well as on the degree of oligomerisation. Macromonomers with high amounts of L-lactide units are partially crystalline.     

Total syntheses of the highly potent anti-cancer polyacetylenes, (S)-18-hydroxyminquartynoic acid, (S)-minquartynoic acid and (E)-15,16-dihydrominquartynoic acid

The total syntheses of three polyacetylenic natural products, (S)-18-hydroxyminquartynoic acid (1), (S)-minquartynoic acid (2) and (E)-15,16-dihydrominquartynoic acid (3), has been achieved. The Cadiot-Chodkiewicz cross-coupling reaction was used as the key step for the construction of tetrayne and triyne units.     

Nickel(II) complexes of methylphosphinediacetic acid

Methylphosphinediacetic acid (H₂G) is coordinated to nickel(II) in two different ways, depending on whether its carboxyl groups are protonated or dissociated. The acid behaves as a monodentate tertiary phosphine in that it yields a series of trans-square planar NiX₂(H₂G)₂ complexes (X = Cl, Br, NCS or CN) which are stable in the solid state and as solutions in polar non-aqueous solvents. In neutral aqueous solution the NiG₂²⁻ complex is the predominant species (logβ₂ = 8.24 at 25°C and I = 0.1) even in excess nickel(II). Solid NiG·4H₂O is the nickel salt of this anion, Ni[NiG₂]·8H₂O. The X-ray structural determination of the barium salt, BaNiG₂·NaClO₄·5H₂O, revealed the uncommon cis-square planar arrangement around nickel with the G₂₋ anions acting as chelating P,O-bidentate to nickel and as O-monodentate to barium. Sodium and perchlorate ions are located between the complex units and, surprisingly, cannot be removed on recrystallization.     

Thermochemistry of sesquiterpene lactone argolide

The enthalpies of dissolution of argolide (C₁₅H₂₀O₃) in 96% ethanol are determined by isothermal calorimetry at 298.15 K and different dilutions of 1: 18 000, 1: 36 000, and 1: 72 000 (by mole). The standard enthalpy of dissolution of argolide in 96% ethanol is calculated from the obtained data: (86 ± 17) kJ mol^?1. The temperature dependence of heat capacity of C₁₅H₂₀O₃ is studied by means of dynamic calorimetry. An equation is derived to describe the С _p ⁰ ~ f (Т) dependence, and the standard heat capacity at 298.15 K is found to be (393 ± 13) J mol^?1 K^?1. The enthalpies of combustion, fusion and formation of argolide are calculated via approximation.     

Microbial Baeyer–Villiger oxidation applied to the synthesis of the N-protected (1R,5R)-Geisman–Waiss lactone

Using whole cell Baeyer–Villiger biooxidation as a key step and depending on the choice of the biocatalyst {E. coli TOP10[pQR239] or Acinetobacter TD63}, the synthesis of nearly enantiopure N-protected (1R,5R)-(−)-Geisman–Waiss lactone (92% ee) or its (1R,5S)-(−) regioisomer (98% ee) be performed.