Pteridine. Teil LXXXI. Mechanismus der Photooxidation von 5,6-Dihydro-1,3-dimethyl-6-thioxopteridin-2,4(1H,3H)-dion

Mechanism of the Photooxidation of 5,6-Dihydro-1,3-dimethyl-6-thioxopteridine-2,4(1H,3H)-dione The mechanism of the photooxidation of 5,6-dihydro-1,3-dimethyl-6-thioxopteridine-2,4(1H,3H)-dione ( 9 ) has been investigated in dependence of the pH. Photooxidation of the anion species in weak alkaline solution takes place by singlet oxygen as well as the superoxide radical anion forming 1,2,3,4-tetrahydro-1,3-dimethyl-2,4-dioxopteridine-6-sulfinate ( 5 ) as the first detectable reaction product. In acidic medium, a more complex photooxidation process is observed leading, in a radical-chain mechanism, to 6,6′-dithiobis[1,3-dimethylpteridine-2,4(1H,3H)-dione] ( 6 ).     

N4-Benzoylspermidine from Oncinotis tenuiloba: Analytical differentiation of the three isomeric N-benzoylspermidines

During the examination of extracts from Oncinotis tenuiloba STAPF a new polyamine, N⁴-benzoylsperimidine ( 8 ), was isolated. For unambiguous structure elucidation, it was transformed into the diacetyl derivative 13 , and the three possible N-benzoyl-substituted isomers of spermidine 5, 8 , and 11 together with their peracetylated derivatives 12–14 , respectively, were synthesized and identified.     

Palladium salicylaldimine complexes containing boronate esters

Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na₂PdCl₄ afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes.Condensation of salicylaldehyde (2-HOC₆H₄C(O)H) with H₂NC₆H₄Bpin (pin=1,2-O₂C₂Me₄) afforded the boron-containing Schiff bases, 2-HOC₆H₄C(H)=NC₆H₄Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na₂PdCl₄ afforded complexes of the type PdL₂ (4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.     

Rapid separation of phenylthiohydantoin amino acids: ambient pressure ion-mobility mass spectrometry (IMMS)

An electrospray ionization (ESI) ambient pressure ion-mobility spectrometer (APIMS) interfaced to an orthogonal reflector time-of-flight mass spectrometer (TOFMS) was evaluated for the first time as a detector for the identification of phenylthiohydantoin (PTH)-derivatized amino acids, the final products in the Edman sequencing process of peptides and proteins. The drift and flight times of the twenty common PTH amino acids were characterized by a well-defined 2-D mobility/mass spectral pattern. The combination of mobility/mass modes of analysis gave rise to a unique trend-line formation for the series of PTH amino acids. In addition, each PTH amino acid had a unique reduced mobility constant K(o), thus enabling the differentiation of all the amino acid derivatives including the PTH-leucine and PTH-isoleucine isomers. More importantly it was shown that it was possible to resolve a complete reference mixture of PTH amino acids in a single experimental run in less than 1 min. Detection limits for the PTH amino acids were found to range from 1.04 to 3.52 ng; indicating that the limits of detection were less than 17.0 pmol for all of the PTH amino acids.     

Synthesis,crystal structure and luminescent property of a novel H<Subscript>2</Subscript>O-bridged cobalt(II) polymer with one-dimensional chain structure

The coordination compound [Co(C₁₀H₇COO)₂(H₂O)₃]_2n · 4nH₂O was prepared by the reaction of 1-naphthoic acid and cobalt(II) acetate tetrahydrate in basic solution, and was fully characterized by X-ray diffraction, element analysis, FTIR, TG-DTA and luminescent spectra. In the crystal the six-coordinated Co(II) centers are linked into one-dimensional zigzag chains by water molecules, which are further assembled into a two-dimensional network through weak inter-chain C–H···π interactions. The solid complex exhibits favorable fluorescent properties similar to those of free ligand at room temperature, which can be assigned to the intraligand electronic transfer.     

Determination of the atomic charge on sodium in sodium salts by numerical integration — a theoretical investigation

The electron density difference in a NaSCN crystal is set up from the ab initio densities of Na⁺ and SCN^? ions and compared to the experimental counterpart based on X-ray diffraction measurements. Numerical integration over the electron density difference is executed around the Na⁺ ion. The atomic charge (+0.20e) derived in this way is in good agreement with the analogous experimental charge (+0.27e) The low experimental value cannot therefore be taken as an indication for a predominantly non-ionic structure of NaSCN and similar sodium salts     

Conversion of 3-benzoyl-1-methyl-4-phenyl-γ-piperidol by arylamines and arylhydrazines. Synthesis of 3-arylamino-1-oxo-1-phenylpropanes and 1,3-diarylpyrazoles and their fragmentation under electron impact

It has been established that on heating, 3-benzoyl-4-hydroxy-1-methyl-4-phenylpiperidine is ring-opened in the presence of arylamines by a type of retroaldol reaction, with subsequent transamination of the intermediate Mannich base and the formation of 3-arylamino-1-oxo-1-phenylpropanes. When using arylhydrazines this γ-piperidol is recyclized with the formation of 1,3-diarylpyrazoles and their 4,5-dihydro derivatives. The mass spectral behavior of a series of 3-arylamino-substituted 1-phenylpropanones has been studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1486–1495, October, 2007.     

The Effect of Alkane Chain Length on the Liquid–Liquid Critical Temperatures of Oligostyrene/Linear-Alkane Mixtures

Summary. Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N ₁=5) to pentacontane (N ₁=50)) with an oligostyrene (1241amu, N ₂=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains.     

Amidine als Zwischenprodukte bei Umamidierungsreaktionen. 9. Mitteilung über Umamidierungsreaktionen

Amidines as Intermediates in Transamidation Reactions By loss of water in the presence of p-toluenesulfonic acid/xylole N-aminoalkyllactames form bicyclic amidines. The corresponding N-alkylaminoalkyl-lactames' react to bicyclic amidinium salts or to transamidated products, ring-enlarged by the N-alkylamino residue, respectively (s. Scheme 1). The bicyclic amidines and amidinium salts are partially hydrolyzed by KOH/H₂O to lactames (s. Scheme 2). Which of the two possible isomeric lactames are formed is discussed.