Indirect determination of micro amounts of medicinal drugs by atomic-absorption spectrometry-measurement of L-ascorbic acid

Summary Indirect determination of medicinal drugs by atomic-absorption spectrometry is reported. The principle of the method is (1) metal chelate formation, and (2) solvent extraction, (3) AAS determination of the metal. The paper describes the determination of L-ascorbic acid by the reduction of the Cu²⁺-neocuproine chelate to the Cu⁺-neocuproine chelate, which is extracted into chloroform in the presence of nitrate.

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Indirekte Bestimmung von Mikromengen Arzneimittel durch Atomabsorptions-Spektrometrie

Zusammenfassung Die indirekte Bestimmung von Arzneimitteln durch AAS wurde beschrieben. Das Prinzip der Methode besteht in der Bildung eines Metallchelates, der Extraktion mit einem Lösungsmittel und der AAS-Bestimmung des Metalls. Beschrieben wurde die Bestimmung der Askorbinsäure durch Reduktion des Kupfer(II)-Neocuproin-Chelates zu der entsprechenden Cu(I)-Verbindung, die in Gegenwart von Nitrat mit Chloroform extrahiert wird.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Synthesis and reaction of 6-substituted 3-methoxycarbonyl-4-methylthio-2H-pyran-2-one derivatives

Reaction of aryl and styryl methyl ketones 1a-m with dimethyl bis(methylthio)methylenemalonate ( 2 ) in the presence of potassium hydroxide in dimethyl sulfoxide gave the corresponding methyl 6-aryl- and 6-styryl-4-methylthio-2-oxo-2H-pyran-3-carboxylates 3a-m . 6-Aryl derivatives 3a-d,g were treated with sodium methoxide in methanol to give the corresponding 6-aryl-4-methoxy-2H-pyran-2-ones 8a-d and 9. Phenylcoumalin ( 7a ) and paracotoin ( 7b ) were synthesized by the desulfurization of 6-aryl-4-methylthio-2H-pyran-2-ones 4a,b. Similarly, anibine ( 8e ) was also synthesized from 3g . Treatment of 3 with hydrogen peroxide or 3-chloroperoxybenzoic acid gave the corresponding 4-methylsulfiny-2H-pyran-2-ones 10a-f in good yields. Displacement reactions of 10a-f with nucleophilic reagents are also described.     

Base-catalyzed polymerization of acryloyl- and methacryloyl-α-amino acid amides

N-Acryloylglycinamide, N-methacryloylglycinamide, N-acryloyl-DL - and L -alaninamide, and N-methacryloyl-DL - and -L -alaninamide were polymerized by basic catalysts. Polymers with low viscosities were obtained. Automatic amino acid analyses of the hydrolyzates of these polymers indicated that a hydrogen transfer from the terminal amide group took place along with vinyl polymerization. Hydrogen transfer from the secondary amide group was also observed. The ratio of the hydrogen transfer and the vinyl polymerizations was determined by results of automatic amino acid analyses.     

Intramolecular rearrangement for regioselective complexation by intramolecular CH/pi interaction in a hydrophobic cavity of a ruthenium coordination sphere

A Ru(II) complex with a hydrophobic cavity formed from two 1-naphthoylamide groups was prepared. Its reactions with beta-diketones gave beta-diketonato complexes in which hydrophobic pi-pi or CH/pi interactions were confirmed by NMR spectroscopy and X-ray crystallography. In the case of the asymmetric beta-diketone benzoylacetone, an isomer with a CH/pi interaction was afforded as the sole product owing to thermodynamic control. The reaction was found to involve a novel intramolecular rearrangement from the phenyl-included isomer to the methyl-included one without rupture of Ru-beta-diketonato coordination bonds (activation energy 52 kJ mol(-1)). This indicates that CH/pi interactions can be more favored thermodynamically than pi-pi interactions in a suitable hydrophobic environment.     

Polarized ethylene. V. Synthesis of 1-substituted indolizine,pyrazolo[1,5-a]pyridine,and their related compounds using methoxyethylene derivatives

The reaction of pyridinium or isoquinolinium N-ylides with methoxy-substituted ethylenes gave the corresponding indolizine and pyrrolo[2,1-a]isoquinoline derivatives bearing acetyl, aroyl, cyano, ester group at the 1-position in one step. Pyrazolo[1,5-a]pyridine, pyrazolo[1,5-a]quinoline, and pyrazolo[5,1-a]isoquinolines were also synthesized in good yields from the corresponding aromatic N-imines and methoxyethylene derivatives.     

Activation of organozinc reagents with t-Bu-P4 base for transition metal-free catalytic SN2' reaction

The t-Bu-P4 base was found to be an excellent catalyst for activating organozinc reagents and was used to promote the S(N)2' reaction of alpha,beta-unsaturated esters bearing a gamma-chloride using various organozinc reagents: these reactions proceeded in high yields with excellent chemo-and regioselectivity.     

Synthesis of multisubstituted 2-(dihydrofuran-2(3H)-ylidene)acetates via intramolecular carboalkoxylation by platinum-olefin catalyst system

The cyclization of 6-(1-alkoxyethyl)hex-2-ynoates in the presence of a platinum-olefin catalyst system gave the corresponding multisubstituted 2-(dihydrofuran-2(3H)-ylidene)acetates in good to high yields. The Z/E selectivity is controlled by the electronic property of the ester group; the 2,2,2-trichloroethyl ester led to the Z isomer, while the phenyl ester gave the E isomer.     

Chirality transfer in gold-catalyzed carbothiolation of o-alkynylphenyl 1-arylethyl sulfides

Chirality transfer in gold-catalyzed carbothiolation of o-alkynylphenyl 1-arylethyl sulfides 1 proceeded with retention of the configuration at the 1-arylethyl group. This result suggests that the [1,3] migration of 1-arylethyl group proceeds through formation of the contact ion pair B followed by C-C bond formation.     

Construction of Chemical‐Responsive Supramolecular Hydrogels from Guest‐Modified Cyclodextrins

A methodology for preparing supramolecular hydrogels from guest‐modified cyclodextrins (CDs) based on the host–guest and hydrogen‐bonding interactions of CDs is presented. Four types of modified CDs were synthesized to understand better the gelation mechanism. The 2D ROESY NMR spectrum of β‐CD‐AmTNB (Am=amino, TNB=trinitrobenzene) reveals that the TNB group was included in the β‐CD cavity. Pulsed field gradient NMR (PFG NMR) spectroscopy and AFM show that β‐CD‐AmTNB formed a supramolecular polymer in aqueous solution through head‐to‐tail stacking. Although β‐CD‐AmTNB did not produce a hydrogel due to insufficient growth of supramolecular polymers, β‐CD‐CiAmTNB (Ci=cinnamoyl) formed supramolecular fibrils through host–guest interactions. Hydrogen bonds between the cross‐linked fibrils resulted in the hydrogel, which displayed excellent chemical‐responsive properties. Gel‐to‐sol transitions occurred by adding 1‐adamantane carboxylic acid (AdCA) or urea. ¹H NMR and induced circular dichroism (ICD) spectra reveal that AdCA released the guest parts from the CD cavity and that urea acts as a denaturing agent to break the hydrogen bonds between CDs. The hydrogel was also destroyed by adding β‐CD, which acts as the competitive host to reduce the fibrils. Furthermore, the gel changed to a sol by adding methyl orange (MO) as a guest compound, but the gel reappeared upon addition of α‐CD, which is a stronger host for MO.