V. A. Al’fonsov

Glycosides from Stevia rebaudiana

A new laboratory method for isolating the glycosides stevioside and rebaudiosides A and C from leaves of Stevia rebaudiana was proposed. According to HPLC, the glycoside contents in plants grown in Russia (Voronezh Oblast’) and Ukraine (Crimea) were 5–6% (stevioside) and 0.3–1.3% (rebaudiosides A and C).

Chemically modified electrodes with amperometric response in enantioselective analysis

Estimation of the enantiomeric purity of chiral biologically active compounds, as well as the determination of particular optical isomers, is very important for the control of medicines, food, and biological fluids. The main approaches to the development of electrochemical enantioselective sensors with the amperometric detection of the signal are considered in this review. Examples of the use of biochemical and supramolecular receptors providing enantiomer recognition and techniques of their inclusion into the corresponding sensors are given. The main characteristics of enantioselective sensors for the determination of optically active medicines, organic acids, aminoacids, carbohydrates, alcohols, and other biologically important compounds are considered.

Reaction of isosteviol diterpenoid with selenium dioxide

Diterpenoid isosteviol was oxidized by selenium dioxide in acetic anhydride or in a mixture of acetic anhydride with dioxane to 15-oxo-derivative, whereas reaction with SeO2 in boiling ethanol led to a mixture of mono- and diselenides. Molecular structure of the monoselenide is established by the X-ray structural analysis.

Alkylation of the isosteviol terpenoid and its oxime with dibromoalkanes in the KOH-DMSO system

The reaction of 16-hydroximinoisosteviol with dihaloalkanes in the KOH-DMSO results in coupling of two isosteviol carcasses by the carboxy groups. The same products were previously synthesized by hydroximination of isosteviol diesters.

Membrane transport of dicarboxylic and α-hydroxy carboxylic acids induced by α-amino phosphonates

New α-amino phosphonates containing different alkyl and aryl substituents at the α-carbon atom were synthesized in high yields by the Kabachnik—Fields and Pudovik reactions. These compounds were studied as carriers of several α-hydroxy carboxylic and dicarboxylic acids through liquid impregnated membranes. These α-amino phosphonates studied are capable of molecular recognition of oxalic acid among structurally similar α-hydroxy carboxylic and dicarboxylic acids. The efficiency and selectivity of mass transfer of oxalic acid increase with an increase in the lipophilicity of the α-amino phosphonate.

Phosphorylation of Betti bases

Reaction of N-substituted 1-(α-aminobenzyl)-2-naphthols (Betti bases) with phosphorus(III) compounds followed by sulfurization afforded new cyclic phosphorylated and thiophosphorylated diastereomeric derivatives of N-substituted Betti bases. In most cases individual diastereomers were isolated and their characteristic spectral features were determined.

Reaction of R-(+)-2-benzylideneaminobutan-1-ol with ethylene phosphorochloridite. Stereospecific formation of (3R,5R)-2-(2-chloroethoxy)-5-ethyl-2-oxo-3-phenyl-1,4,2-oxazaphosphorinane

The reaction of R-(+)-2-benzylideneaminobutan-1-ol with ethylene phosphorochloridite afforded phosphorus-epimeric (3R,5R)-2-(2-chloroethoxy)-5-ethyl-2-oxo-3-phenyl-1,4,2-oxazaphosphorinanes. The phosphorinane-ring closure proceeded stereospecifically and occurred only from one of the diastereofacial sides (re) of the C=N bond.

Metal derivatives of diterpenoid isosteviol

Metal salts (including transition metals salts) of chiral natural diterpenoid isosteviol and its hydrophosphoryl derivative were obtained for the first time. The compounds obtained can be used in pharmaceutics, metal catalysis, and also for creating new materials with magnetic properties.

Reaction of β-iminoalcohols with sulfur dioxide. Synthesis of (±)-(2-hydroxyalkylamino)phenyl(isopropyl)-methanesulfonic acids

Reactions of 2-(N-isopropylidene)amino-2-methylpropanol, 2-(N-benzylidene)-, and 2-(N-isopropylidene) aminoethanols with sulfur dioxide in aqueous ethanol medium produce (±)-(2-hydroxyalkylamino)-phenyl(isopropyl)methanesulfonic acids. Structure of (±)-(2-hydroxyethylamino)phenylmethanesulfonic acid was determined by X-ray diffraction method.

Reaction of O,O-diethyl phosphorodithioic acid with hexadec-1-ene. Catalysis with zinc chloride

As shown earlier [1–6] the regiochemistry of addition of O,O-diethyl phosphorodithioic acid (I) to unsymmetrical alkenes, i.e. formation of Markovnikov or anti-Markovnikov products, is defined by the nature of substituents at the double bond and, in some cases, on the presence or absence of catalysts in the reaction mixture. Alkenes with electron-acceptor groups at the double bond take up dithio acid I under base catalysis or without it occurs against Markovnikov’s rule [2]. The reactions of unactivated aliphatic alkenes (oct-1and oct-2-enes, cyclohexene, diisobutylene) at 100°C give rise to Markovnikov products [4–6]. Phos-phorodithioc acids not been subjected to special purification with aqueous sodium carbonate [4–6] contain an admixture of phosphorus sulfide (P4S10) which can destroy peroxide admixtures in commercial alkenes and thus favors formation of Markovnikov products. At the same time, cumene hydroperoxide additive in a mixture of dithio acid I and oct-1-ene favors an antiMarkovnikov reaction pathway. The reaction of commercial oct-1-ene (with a natural content of peroxides) with purified dithio acid I provides a mixture of two isomeric Markovnikov adducts [6].