Direct synthesis of hetero-biaryl compounds containing an unprotected NH2 group via Suzuki-Miyaura reaction

Hetero-biaryl compounds were prepared via the Suzuki-Miyaura coupling reaction of hetero-aryl moieties containing an unprotected NH₂ group and arylboronic acids. D-t-BPF was found to be an efficient ligand for the cross-coupling of NH₂-unprotected hetero-aryl chlorides with phenylboronic acid.     

Four new cycloartane glycosides from Aquilegia vulgaris

Four new cycloartane glycosides, named aquilegiosides G-J, were isolated from the dried aerial parts of Aquilegia vulgaris. Their structures were determined by spectroscopic analysis and chemical evidence.     

Asymmetric sequential Michael reaction: Synthesis of optically active bicyclo[2.2.2]octane derivatives

The sequential Michael reaction of (S)-4,5-di-O-isopropylidenepent-2- enoate and with lithium enolate afforded diastereo- and enantioselectively bicyclo[2.2.2]octane and (or ), respectively. The adducts were efficiently converted into both enantiomeric keto aldehydes (−)- and (+)- .     

Chain length effect of the counterion on the partial molal volume of alkanesulfonates

The partial molal volumes of two series of homologous surfactants, n-alkylammonium decanesulfonates and a, ?-alkanediammonium nonanesulfonates, were measured below and above their CMC in aqueous solution. Their counterions were n-alkylammonium and a, ?-alkanediammonium. The relationship between the partial molal volume and the chain length of the counterion below the CMC had an inflection point. The relationship between them, above the CMC, was almost linear. In the case of the alkylammonium salts, the values of the volume change of micellization were almost the same when the chain length of the counterions was shorter than the butyl, and increased with an increase in the chain length when it was longer than the propyl. In the case of the alkanediammonium salts, the volume change of micellization showed a small decrease with the chain length when it was shorter than octane, and was very large for the nonane ammonium salt. The large positive increase in the volume change with the increase in the chain length of the counterion can be explained by the hydrophobic interaction between the alkyl chain of the counterion and the hydrophobic core of the micelle.     

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.     

Syntheses and structures of mono-, di- and tetranuclear rhodium or iridium complexes of thiacalix[4]arene derivatives

The reactions of [Cp*MCl2]2(Cp*=eta5-C5Me5, M = Rh, Ir) with thiacalix[4]arene (TC4A(OH)4) and tetramercaptothiacalix[4]arene (TC4A(SH)4) gave the mononuclear complexes [(Cp*M){eta3-TC4A(OH)2(O)2}] and the dinuclear complexes [(Cp*M)2{eta3eta3-TC4A(S)4}] respectively, while the analogous reactions with dimercaptothiacalix[4]arene (TC4A(OH)2(SH)2) produced the tetranuclear complexes [(Cp*M)2(Cp*MCl2)2-{eta3eta3eta1eta1-TC4A(O)2(S)2}].     

Application of AMS <Superscript>14</Superscript>C measurements to criminal investigations

¹⁴C variations of atmospheric CO₂ as well as carbonaceous fraction of living materials, such as collagen from tooth and bone, tissue, skin, hair, nail, etc., of modern humans are influenced by ¹⁴C produced artificially by nuclear bomb tests in the atmosphere from late 1950s to early 1960s. By careful investigation of ¹⁴C concentration of tree rings and human body samples formed in this time intervals, we can establish a relationship of their ¹⁴C concentrations with calendar year. By applying this relation to a sample whose ¹⁴C concentration can be measured, we can estimate the formation age of the sample. In addition, sources of the chemicals that were used in some criminal cases can be possibly identified, by their carbon isotope ratios (¹³C/¹²C and ¹⁴C/¹²C). This method of age determination has been applied to a forensic study, i.e., two criminal cases of murder. For each case, by comparing the measured ¹⁴C abundances of several pieces of hair and one tooth (the third molar) from the body with the annual change on concentrations of bomb-produced ¹⁴C, the time of death of the body and the age of the victim were estimated. The estimated values were consistent with the real ones that were revealed by the confession of the real murderers.     

Methane Decomposition in a Barium Titanate Packed-Bed Nonthermal Plasma Reactor

The behavior of lattice oxygen species of the ferroelectric material during methane oxidation was investigated using a nonthermal plasma reactor packed with BaTiO ₃ pellets. Lattice oxygen species in BaTiO ₃ play an important role in the formation of N ₂ O and the oxidation of CH ₄ . The oxidation products such as CO and CO ₂ were formed from independent reaction pathways. Lattice oxygen species were able to preferentially oxidize the carbon species deposited on the pellet surface into CO. Also, N ₂ O and NO _x were independently formed in the N ₂–O ₂ reaction, suggesting that different oxygen species give N ₂ O and NO _x. N ₂ O was produced by the oxidation of molecular nitrogen with lattice oxygen species.     

A synthesis of chiral 1,1,3-trisubstituted 1,2,3,4-tetrahydro-beta-carbolines by the Pictet-Spengler reaction of tryptophan and ketones: conversion of (1R,3S)-diastereomers into their (1S,3S)-counterparts by scission of the C(1)-N(2) bond

The Pictet-Spengler cyclization of the imines (3) prepared by the condensation of L-tryptophan methyl ester (1) and aryl methyl ketones (2), using titanium(IV) isopropoxide as an iminating reagent, quantitatively proceeded, when treated with trifluoroacetic acid (TFA) or formic acid, to provide two diastereomers, that is (1S,3S)-1-aryl-3-isopropoxycarbonyl-1-methyl-1,2,3,4-tetrahydro-beta-carbolines (4) and their (1R,3S)-diastereomers (5), of which the diastereomer ratios varied from 1 to 5 depending on the reaction conditions. The (1R,3S)-diastereomers (5) are thermodynamically more stable than their (1S,3S)-congeners (4), as shown by equilibration experiments in TFA. The conversion of 4 to 5 (also 5 to 4) should occur under acidic conditions by cleavage of the C(1)-N(2) bond with complete retention of configuration at the C-3 chiral center. The low diastereo-selectivity observed in the Pictet-Spengler reaction of 1 and 2 is concluded to be a stereochemical outcome under conditions of kinetic control (lower temperature, shorter reaction time), while the high diastereo selectivity with preferential formation of the more stable isomer (5) is the result of thermodynamically controlled experiments (higher temperature, longer reaction time).     

Intramolecular catalytic Friedel-Crafts reactions with allenyl cations for the synthesis of quinolines and their analogues

[reaction: see text] This paper describes a novel method to synthesize a quinoline backbone by incorporating allenyl cations into a catalytic intramolecular Friedel-Crafts reaction. The initial products were isomerized and aromatized upon treatment with acid and base, respectively, to give quinolines. The basic concept also proved to be promising for 1-benzazepine, 1-benzazocine, or isoquinoline synthesis.