Spontaneously formed trans-anethol/water/alcohol emulsions: mechanism of formation and stability

We studied the spontaneous emulsification and droplet growth mechanism in trans-anethol/water/ethanol solutions, also known as the beverage ouzo, using dynamic light scattering spectroscopy. This simple ternary mixture is a generic example of a system that forms microemulsions spontaneously when brought into the two-phase region. The volume fraction of the dispersed phase was found to profoundly affect the growth rates of the droplets, which is a new finding that has not been predicted by the Lifshitz-Slyozov-Wagner theory. Time-dependent measurements show that the droplet growth is governed by Ostwald ripening (OR), and no coalescence was observed. Furthermore, the OR rates increase with increasing oil concentration at low alcohol content. We attribute this behavior to enhanced droplet-droplet interactions. At high ethanol concentrations, we found that the measured rates decreased as the oil concentration increased. The OR growth mechanism completely correlates with changes in droplet size. The kinetics of droplet growth shows that the ripening has a saturation limit at a droplet radius of about 1.5 mum. Thus, formed emulsions remain stable for months.     

Covalently bonded platinum(II) complexes of alpha-amino acids and peptides as a potential tool for protein labeling

Arylplatinum(II) complexes have been covalently bonded to the N and C termini and to the alpha-carbon of various amino acid derivatives. These organometallic-functionalized amino acid compounds can be converted into the corresponding free amino acids under both basic and acidic conditions; this demonstrates the excellent stability properties of these biomolecules. Due to the NMR activity displayed by the 195Pt nucleus (natural abundance 33.8%, I = 1/2) these compounds are functional bio-markers. Furthermore, the ability of the arylplatinum functional group to bind SO2 gas, selectively and reversibly as indicated by changes in the spectroscopic properties (1H, 13C, 195Pt NMR and UV spectra) of these compounds, allows for the potential use of these complexes as in vitro biosensors.     

Ferrocenyltrithiocarbonates : I. Direct access from α-ferrocenylcarbinols by a SNi mechanism. Absolute x-ray structure determination of (R)-ferrocenylmethylmethane S-methyl-trithiocarbonate

¹⁰³Rh Chemical shifts of a variety of mono- and di-nuclear rhodium carbonyl complexes are reported together with the modifications to the probe and decoupler unit of a JEOL PS-100 PFT spectrometer which enable these ¹⁰³Rh-decoupled ¹³C NMR measurements to be made. These data are discussed in conjunction with ¹³C NMR data on other rhodium carbonyls.     

THE EXCITATION OF 8-METHOXYPSORALEN WITH VISIBLE LIGHT: REVERSED PHASE HPLC QUANTITATION OF MONOADDUCTS and CROSS-LINKS

Abstract— The formation of 8-methoxypsoralen-DNA monoadducts and cross-links is presumed to be responsible for the efficacy of photochemotherapies that employ 8-methoxypsoralen activated with long-wavelength ultraviolet radiation (UVA,320–400 nm). In this report it is shown that 8-methoxypsoralen can also be activated with visible light (419 nm). Bovine aorta smooth muscle cells were treated with 8-methoxypsoralen (1000 ng/mL) and 419 nm light (up to 12 J/cm²). Cellular DNA was isolated, hydrolyzed using nucleolytic enzymes and then analyzed by reversed-phase high-performance liquid chromatography. The primary effect of using visible light instead of long-wavelength ultraviolet radiation is a more than 10-fold reduction in the extent of cross-link formation. Because the extent of monoadduct and cross-link formation has not been routinely measured in experiments in which cellular assays have been performed, it is difficult to correlate cell response to the presence of a particular type of 8-methoxypsoralen photoadduct (monoadduct or cross-link). Thus, the use of visible light allows the study of cells containing nearly 100% monoadducts. In addition, the reduction in cross-link formation when visible light is used to activate the compound may also reduce the mutagenicity of 8-methoxypsoralen and hence enhance its therapeutic efficacy.     

Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone

Achiral P‐donor pincer‐aryl ruthenium complexes ([RuCl(PCP)(PPh₃)]) 4c , d were synthesized via transcyclometalation reactions by mixing equivalent amounts of [1,3‐phenylenebis(methylene)]bis[diisopropylphosphine] ( 2c ) or [1,3‐phenylenebis(methylene)]bis[diphenylphosphine] ( 2d ) and the N‐donor pincer‐aryl complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 2). The same synthetic procedure was successfully applied for the preparation of novel chiral P‐donor pincer‐aryl ruthenium complexes [RuCl(P*CP*)(PPh₃)] 4a , b by reacting P‐stereogenic pincer‐arenes (S,S)‐[1,3‐phenylenebis(methylene)]bis[(alkyl)(phenyl)phosphines] 2a , b (alkyl=ⁱPr or ^tBu, P*CHP*) and the complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 3). The crystal structures of achiral [RuCl(equation/tex2gif-sup-3.gifPCP)(PPh₃)] 4c and of chiral (S,S)‐[RuCl(equation/tex2gif-sup-6.gifPCP)(PPh₃)] 4a were determined by X‐ray diffraction (Fig. 3). Achiral [RuCl(PCP)(PPh₃)] complexes and chiral [RuCl(P*CP*)(PPh₃)] complexes were tested as catalyst in the H‐transfer reduction of acetophenone with propan‐2‐ol. With the chiral complexes, a modest enantioselectivity was obtained.     

A new family of small molecules to probe the reactivation of mutant p53

Cells that express mutant p53 derived from cancers are selectively killed by a new class of small organic molecules. The protein p53 is recognized as one of the most important guardians in the body that prevents tumor development. Mutant forms of p53 are present in approximately 50% of all human cancers. Molecules that selectively kill cells expressing mutant p53 could become important chemotherapeutic agents. Our research focuses on developing a synthetically accessible class of molecules that can be easily modified to examine structural activity relationships and mechanism of biological activity or to optimize for anticancer activity. In this communication, a new class of molecules that selectively arrests growth of cells expressing two forms of mutant p53 is described. Synthetic routes to these compounds are also presented.     

α-Diimines as monodentate or bridging ligands; synthesis and characterization of palladium(II) and rhodium(I) di(t-butyl)diimine complexes

Complexes of di(t-butyl)diimine with PdCl₂(PhCN)₂ and with (CO)₂RhCl dimer have been synthesized and characterized. The diimine ligand is monodentate bonded in PdCl₂(t-butyldiimine)₂, while in (t-butyldiimine)-[Rh(CO)₂Cl]₂ it bridges two Cl(CO)₂Rh units.     

Double silyl migration converting ORe[N(SiMe(2)CH(2)PCy(2))(2)] to NRe[O(SiMe(2)CH(2)PCy(2))(2)] substructures

The reaction of (R(2)PCH(2)SiMe(2))(2)NM (PNP(R)M; R = Cy; M = Li, Na, MgHal, Ag) with L(2)ReOX(3) [L(2) = (Ph(3)P)(2) or (Ph(3)PO)(Me(2)S); X = Cl, Br] gives (PNP(Cy))ReOX(2) as two isomers, mer,trans and mer,cis. These compounds undergo a double Si migration from N to O at 90 degrees C to form (POP(Cy))ReNX(2) as a mixture of mer,trans and fac,cis isomers. Additional thermolysis effects migration of CH(3) from Si to Re, along with compensating migration of halide from Re to Si. DFT calculations on various structural isomers support the greater thermodynamic stability of the POP/ReN isomer vs PNP/ReO and highlight the influence of the template effect on the reactivities of these species.     

Asymmetric Synthesis of Calyculin C. 2. Synthesis of the C(26)-C(37) Fragment and Model Wittig Couplings

We report our synthesis of the C(26)-C(37) fragment of serine/threonine protein phosphatase PP1 and PP2A inhibitor calyculin C (1). Outlined in this paper are synthetic approaches to the two components based on disconnection at the C(33)-N(3) amide bond. We report the successful synthesis of the C(33)-C(37) aza-sugar derived from D-lyxose which was coupled onto a C(26)-C(32) aminooxazole originating from L-pyroglutamic acid. Elaboration of the resulting amide to a fully deprotected C(26)-C(37) fragment of calyculin C completed our synthesis. This provided an appropriate phosphonium salt for use in a Wittig olefination for joining both halves of the natural product.     

Stabilisation of [Fe2(CO)9] and [Ru2(CO)9] bu substitution with bridging diphosphorus ligands

Reaction of [Fe₂(CO)₉] with a half molar amount of R₂PYPR₂ (Y = CH₂, R = Ph, Me, OMe or OPrⁱ; Y = N(Et), R = OPh, OMe or OCH₂; Y = N(Me), R = OPrⁱ or OEt) leads to the ready formation of a product which on irradiation with ultraviolet light rapidly decarbonylates to the heptacarbonyl derivative [Fe₂(μ-CO)(CO)₆{μ-R₂PYPR₂}]. Treatment of the latter with a slight excess of the appropriate ligand results, under photochemical conditions, in the formation of the dinuclear pentacarbonyl complex [Fe₂(μ-CO)(C))₄{μ-R₂PYPR₂}₂] but under thermal conditions in the formation of the mononuclear species [Fe(CO)₃{R₂PYPR₂}]. Reaction of [Ru₃(CO)₁₂] with an equimolar amount of (RO)₂PN(R′)P(OR)₂ (R′ = Me, R = Prⁱ or Et; R′ = Et, R = Ph or Me) under either thermal or photochemical conditions produces [Ru₃(CO)₁₀{μ-(RO)₂PN(OR)₂}] which reacts further with excess (RO)₂PN(R′)P(OR)₂ on irradiation with ultraviolet light to afford the dinuclear compound [Ru₂(μ-CO)(CO₄{μ-(RO)₂PN(R′)P(OR)₂}₂]. The molecular structure of [Ru₂(μ-CO)(CO)₄{μ-(MeO)₂PN(Et)P(OMe)₂}₂], which has been determined by X-ray crystallography, is described.