Synthesis of phosphorus (silicon,tin)-containing derivatives of mercaptoketenes and some of their properties

Some newS-phosphorylated,S-silylated, andS-stannylated derivatives of -mercaptoketones were obtained. The reactions of some of these compounds induced by the temperature and by molecular oxygen as well as the phosphorylation of the Si- and Sn-containing derivatives were studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 353–357, February, 1995.     

Substituted 1,2-Thiazetidine 1,1-Dioxides. Synthesis of (<Emphasis Type="Italic">RS</Emphasis>)- and (<Emphasis Type="Italic">S</Emphasis>)-1,2-Thiazetidine-3-acetic Acid 1,1-Dioxide and its Reactions with Amino Acids and Dipeptides

Summary. (RS)-2-tert-Butyldimethylsilyl-1,2-thiazetidine-3-acetic acid 1,1-dioxide prepared from (RS)-S-benzyl--homocysteine was condensed via DCC/NHS with various L-amino acid esters or dipeptide esters yielding N-silylated -sultam peptides. A -sultam active ester was isolated as an intermediate. Desilylation with TBAF in THF yielded stable N-unsubstituted products, and deprotection of the benzyl esters was achieved by catalytic hydrogenation. (S)-S-Benzyl--homocysteine was obtained by fractional crystallization of the brucine salt of the racemate and transformed into benzyl (S)-1,2-thiazetidine-3-acetate, which was on the other hand synthesized by an enantiospecific route from -benzyl Boc-L-aspartate. Some -sultam peptides were prepared from the (S)-enantiomer, and finally some -sultam peptides containing D-Ala units were obtained.     

Chiral β-hydroxycarbonyl compounds based on (−)-menthone: structure and behavior in liquid crystalline systems

It has been established by X-ray structural analysis that 2-(1-biphenyl-4-yl-1-hydroxy)methyl-p-menthan-3-one, one of the products of the reaction of (–)-menthone triisopropyloxytitanium enolate with 4-phenylbenzaldehyde, has a 1R,2S,4S,1S configuration. In crystals, this -hydroxyketone adopts a chair conformation with equatorial methyl and isopropyl groups and an axial 2-(1-biphenyl-4-yl-1-hydroxy)methyl substituent. Unlike the stereoisomeric compound with the 1R,2S,4S,1S configuration, the exocyclic fragment of which has an intramolecular >C=O...H-O- hydrogen bond in crystals and solutions, in the crystals of the 1R,2S,4S,1S ketol under study, molecules are linked by a network of cooperative -O-H...O-H...O-H... hydrogen bonds. Based on the results of molecular mechanics calculations and experimental data of¹H NMR and IR spectroscopy, conformations of molecules of this compound, which are in equilibrium in solution, have been characterized. Based on data on spatial structures of stereoisomeric -hydroxyketones and the character of H-bonds formed by these compounds, the characteristic features of the effect of these chiral alloying additives on the supramolecular structure and macroscopic properties of liquid crystalline systems have been interpreted.The results of a study of stereoselectivity of the reactions of different (–)-menthone enolates with aromatic aldehydes will be published later.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1247–1255, July, 1995.The work was supported by the Foundation for Basic Research of the State Science and Engineering Committee of Ukraine (Project No. 93-3.2/75).     

Antioxidant Study and Assignments of NMR Spectral Data for 3′,4′,7-Trihydroxyflavanone 3′,7-Di-O-β-D-glucopyranoside (Butrin) and Its Hydrolyzed Product

The NMR spectral data including high resolution ¹H, ¹³C and 2D NMR for butrin, 3,4,7-trihydroxyflavanone 3,7-di-O--D-glucopyranoside, isolated from flowers of Butea monosperma, are reported here for the first time. Butrin was hydrolyzed using b-glucosidase to butin in high yield. They were subjected to free radical scavenging test using 2,2-diphenyl-1-picrylhydrazyl (DPPH) spectrophotometric assay. At a dose of 4 × 10^-8 mol of tested compounds, the percentage of reduced DPPH for butin was 14.5% while no reduction was observed for butrin (0%).     

Asymmetrical synthesis of organometallic analogs of natural compounds. 8. Reactions of pentafluorobenzaldehyde with the Ni(II) complex of a schiff base of glycine and (S)-2-[N-(benzylprolyl)amino]benzophenone

Reaction of pentafluorobenzaldehyde with a Ni(II) complex of a Schiff base formed from glycine and (S)-2-[N-(benzylprolyl)amino]benzophenone yields, depending on the reaction conditions, the hitherto unknown, diastereo-and enantiomerically pure amino acids 2R,3S--(4-methoxytetrafluorophenyl)serine, 2S,3R--(4-methoxytetrafluorophenyl)serine, 2S,3S--(pentafluorophenyl)serine, and 2S,3R--(pentafluorophenyl)serine.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Institute of Bioorganic Chemistry and Petroleum Chemistry, Ukrainian Academy of Sciences, 252028 Kiev. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 687–693, March, 1992.     

Highly conformationally constrained halogenated 6-spiroepoxypenicillins as probes for the bioactive side-chain conformation of benzylpenicillin

Summary The halogenated 6-spiroepoxypenicillins are a series of novel semisynthetic-lactam compounds with highly conformationally restricted side chains incorporating an epoxide. Their biological activity profiles depend crucially on the configuration at position C-3 of that epoxide. In derivatives with aromatic-containing side chains, e.g., anilide, the 3R-compounds possess notable Gram-positive antibacterial activity and potent-lactamase inhibitory properties. The comparable 3S-compounds are antibacterially inactive, but retain-lactamase inhibitory activity.Using the molecular simulation programs COSMIC and ASTRAL, we attempted to map a putative, lipophilic accessory binding site on the PBPs that must interact with the side-chain aromatic residue. Comparative computer-assisted modelling of the 3R, and 3S-anilides, along with benzylpenicillin, indicated that the available conformational space at room temperature for the side chains of the 3R and the 3S-anilides was mutually exclusive. The conformational space for the more flexible benzylpenicillin could accommodate the side chains ofboth the constrained penicillin derivatives. By a combination of van der Waals surface calculations and a pharmacophoric distance approach, closely coincident conformers of the 3R-anilide and benzylpenicillin were identified. These conformers must be related to the antibacterial, bioactive conformer for the classical-lactam antibiotics. From these proposed bioactive conformations, a model for the binding of benzylpenicillin to the PBPs relating the three-dimensional arrangement of a putative lipophilic S₂-subsite, specific for the side-chain aromatic moiety, and the 3-carboxylate functionality is presented.This work has been reported in preliminary form at the 4th Royal Society of Chemistry International Symposium on Recent Advances in the Chemistry of-lactam Antibiotics, Churchill College, Cambridge, U.K., 3–6 July 1988.     

Synthesis of α-tocopherol analogs with unsaturated side chain and their transformation into the corresponding chromans with ω-functionalized side chain

-Tocopherol analogs with double bond-containing side chains were synthesized by condensation of trimethylhydroquinone with optically active (3R/S,4S)-3,4,8-trimethylnona-1,7-dien-3-ol and linalool in the presence of the zeolite-containing Tseokar-10 aluminosilicate. Ozonolysis of these compounds gave the corresponding chromans with -formyl or (after hydride reduction) -hydroxyl groups in the side chain.     

Triterpene Glycosides from Plants of the Astragalus Genus. Structure of Cyclounifolioside A from Astragalus unifoliolatus

The known compound oleanolic acid (1) and a new cycloartane glycoside cyclounifolioside A (2), which has the structure 6,16-di-O-acetyl-24R-cycloartan-6,16,24,25-pentaol 3-O--D-glucopyranoside, were isolated from Astragalus unifoliolatus Bunge. The structures of the isolated compounds were established using chemical transformations and two-dimensional spectra (TOCSY, ROESY, HMBC, HSQC, COSY).     

Triterpene Glycosides from Plants of the Astragalus Genus. III. Structure of Cyclounifolioside C from Astragalus unifoliolatus

The known compound cyclocantogenin (1) and a new cycloartane glycoside cyclounifolioside C (2), which has the structure 24R-cycloartan-3,6,16,24,25-pentaol 3-O--D-glucopyranoside, were isolated from roots of Astragalus unifoliolatus Bunge. The structures of the isolated compounds are established using hydrolysis and spectral data.     

Terpenes in organic synthesis

A seven-step synthesis ofS-(+)-hydroprene (S-1) in 20 % overall yield starting fromS-(+)-3,7-dimethyl-1,6-octadiene (2) of 55+-10 % optical purity is described. The introduction of an optical enhancement step in the synthetic sequence at the stage ofS-(–)-3,7-dimethyl-1-octanol (9) raises the optical purity ofS-1 from 50 % to 80 %.For part 13, see. ref.¹ Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 342–348, February, 1993.     

New approach to nonracemic 1-alkylamino-3-aryloxypropan-2-ols belonging to β-blockers via cyclic sulfites

Nonracemic -blockers, viz., (S)-propranolol and (S)-timolol, were prepared from (S)-glycidol in three steps consisting in the reaction with SOCl₂ followed by the reaction of the resulting (4S)-4-chloromethyl-2-oxo-1,3,2-dioxathiolanes with the corresponding phenol and the final cleavage of (4R)-aryloxymethyl sulfites under the action of amines in DMF.     

Tetracyclische Imidazole

2-(Phenacyl)-tetrahydro--carboline (2) was transformed to theE/Z-oximes3 and4 and the isolated species cyclodehydrogenated to the nitrone5 and oxadiazine6. These compounds were dehydrated in acidic medium to the imidazole9.

     

Stereoselective dimerization of chiral α-bromoamides promoted by Fe(CO)5

Organic -bromocarboxylates react with aldehydes and ketones in the presence of Fe(CO)₅ (the Reformatsky-type reactions). Unlike them, N-oxazolidinone derivatives of the same acids undergo diastereoselective reductive dimerization to give (2S,3S)-dimers, regardless of the configuration of the -chiral center in the starting reagent.     

Linear and cyclic N-acetyl-α-aryl-glycines: Synthesis and chemiluminescence studies

Summary A series of N-acetyl--arylglycines (IIa,IIb) was prepared by acid-induced electrophilic -amidoalkylation reactions; compounds of typeIIb were transformed into the corresponding 3-acetylaminobenzo[b]furan-2(3H)ones (III) by treatment with acetic anhydride. It was found that most of these new compounds (lactones as well as open chain derivatives) undergo base induced oxidation in the presence of oxygen with the emission of visible light. Preliminary structure-activity relationships for these novel chemiluminescence class are proposed.

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Lineare und cyclische N-Acetyl--aryl-glycine: Synthese und Chemilumineszenz-Untersuchungen

Zusammenfassung Eine Reihe von N-Acetyl--arylglycinen (IIa,IIb) konnte durch sauer induzierte elektrophile -Amidoalkylierung hergestellt werden; die Behandlung von Verbindungen des TypsIIb mit Acetanhydrid führte zu den entsprechenden 3-Acetylaminobenzo[b]furan-2(3H)onen (III). Es zeigt sich, daß die Mehrzahl dieser neuen Verbindungen (sowohl Lactone als auch offenkettige Derivate) bei basisch induzierter Oxidation mit (Luft-)Sauerstoff sichtbares Licht emittieren. Erste Struktur-Aktivitäts-Beziehungen für diese neue chemilumineszenzierende Klasse werden vorgeschlagen.

     

Substituent effect and enthalpy-entropy compensation on the inclusion ofβ-cyclodextrin with 1-substituted naphthalenes

The inclusion complexation of-CD with 1-substituted naphthalenes has been investigated by fluorescence spectroscopy. It was observed that the association constants were influenced by the molar refraction (R _m), hydrophobic constant ( _x ), and Hammett constant ( _x ) of substituents in the guest compounds. The thermodynamic parameters G⁰, H ⁰, and S ⁰ determined by measuring the temperature-dependentK _a values shows that inclusion complex formation is enthalpy driven. The results are discussed in terms of enthalpy-entropy compensation.     

Resolution of Δ2-isoxazoline-5-carboxylates by a protease fromAspergillus Oryzae providing masked synthons for enantiopure β-aminoalcohols and related structures

Summary A series of racemic ²-isoxazolinecarboxylates have been synthesized and subjected to enzymatic hydrolysis by a protease fromAspergillus oryzae in a two-phase system. Out of these compounds only isoxazoline-5-carboxylates unsubstituted at C-4 were hydrolyzed. Thus, from 3-ethoxycarbonyl-, 3-methyl-, and 3-phenyl-²-isoxazoline-5-carboxylates the corresponding (R)-configurated carboxylic acids are obtained. In contrast, an additional methyl group at C-5 changes the steric course of the hydrolysis to give predominantly the (S)-acid. The enantioselectivities obtained are in the range ofE=5–35.

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Racematspaltung von ²-Isoxazolin-5-carboxylaten mittels einer Protease vonAspergillus oryzae zur Darstellung maskierter Synthons für enantiomerenreine -Aminoalkohole und verwandte Strukturen

Zusammenfassung Zahlreiche ²-Isoxazolincarbonsäureester wurden in racemischer Form dargestellt und einer enzymatischen Hydrolyse mittels einer Protease ausAspergillus oryzae in einem Zwei-Phasen-System unterworfen. Lediglich an C-4 unsubstituierte Isoxazolin-5-carbonsäureester wurden hydrolysiert. Aus 3-Ethoxycarbonyl-, 3-Methyl- und 3-Phenyl-²-isoxazolin-5-carbonsäureestern wurden die entsprechenden (R)-konfigurierten Carbonsäuren erhalten, während eine zusätzliche Methylgruppe an C-5 eine bevorzugte Bildung der (S)-Säure bewirkte. Die erzielten Enantiomerenüberschüsse liegen im Bereich vonE=5–35.

     

A new hydroquinone diglucoside from <Emphasis Type="Italic">Lysimachia fordiana</Emphasis>

A new hydroquinone diglucoside along with five known compounds was isolated from the whole plant of Lysimachia fordiana Oliv. The structure of the new compound was determined to be 2-heptyl-6-methoxy-1,4-hydroquinone-1,4-di-O--D-glucopyranoside (6). The five known compounds were identified as pentacosane (1), stigmasterol (2), 2-heptyl-6-methoxy-1,4-benzoquinone (3), palmitic acid (4), and rutin (5), respectively. This is the first report of the isolation of Lysimachia fordiana Oliv. in the family Primulaceae.Published in Khimiya Prirodnykh Soedinenii, No. 5, pp. 377–379, September–October, 2004.     

Liquid Chromatographic Resolution of Racemic α-Hydroxycarboxylic Acids on Ligand Exchange Chiral Stationary Phases

Two ligand exchange chiral stationary phases (CSPs) based on (S)-leucinol derivative, sodium N-((S)-1-hydroxymethyl-3-methylbutyl)-N-undecylaminoacetate, and (R)-phenylglycinol derivative, sodium N-((R)-2-hydroxy-1-phenylethyl)-N-undecylaminoacetate, covalently bonded to silica gel have been successfully applied in the resolution of nine -hydroxycarboxylic acids. The latter was more effective than the former, the separation factors () being 1.05 to 2.12 while the resolution factors (R_S) varying from 0.18 to 5.29 on the latter. The chromatographic resolution behaviors were dependent on the type and the content of organic modifier and the content of CuSO₄ in aqueous mobile phase and the column temperature. A possible chiral recognition mechanism was also proposed based on the chromatographic resolution behaviors.     

New dithio-bis-(diaroylmethanes) and acetyl diaroylchloromethyl disulfides: Attractive synthons and precursors for the liberation of highly reactive dithiiranes or thiosulfines

Summary In a new, feasible procedure five symmetricalpara-substituted diaroylmethanes ((4-X-C₆H₄-CO)₂-CH₂;X=F, Cl, Br, CH₃, and CH₃O) are prepared, in most cases in very good yields. For purification and activation, they are converted into the copper(II) complexes of their enolates. Subsequently, three reaction steps with disulfur dichloride (S₂Cl₂), chlorine, and ethanethioic acid yield new CH-acidic dithio-bis-(diaroylmethanes), -chlorosulfenic acid chlorides, and acetyl diaroyl-chloromethyl disulfides. The latter compounds are of interest for the liberation of highly reactive dithiirane/thiosulfine species. With thiomorpholine, -chlorosulfenic acid chlorides give -chlorosulfenic acid amides.

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Neue Dithio-bis-(diaroylmethane) und Acetyl-diaroylchlormethyl-disulfide: attraktive Synthone und Vorläufer zur Freisetzung hochreaktiver Dithiirane oder Thiosulfine

Zusammenfassung In einem neuen, gut handhabbaren Verfahren werden in meist sehr guter Ausbeute fünf symmetrischepara-substituierte Diaroylmethane ((4-X-C₆H₄-CO)₂-CH₂;X=F, Cl, Br, CH₃ und CH₃O) und daraus zur Reinigung und Aktivierung die Kupfer(II)komplexe ihrer Enolate dargestellt. Drei Reaktionsschritte mit Dischwefeldichlorid (S₂Cl₂), Chlor und Thioessigsäure führen der Reihe nach anschließend zu neuen CH-aciden Dithio-bis-(diaroylmethanen), -Chlorsulfensäure-chloriden und Acetyl-diaroylchlormethyl-disulfiden. Die letzteren Verbindungen sind zur Freisetzung von hochreaktiven Dithiiran/Thiosulfin-Spezies von Interesse. Mit Thiomorpholin geben -Chlorsulfensäurechloride -Chlorsulfensäureamide.

     

A structural analysis of the complexes of (S,S)-dimethylpyridino-18-crown-6 with (R) and (S)-[α-(1-naphthyl)ethyl]ammonium perchlorate by NMR techniques and molecular modeling

Significant - interaction is found in the complexes of (S, S)-dimethylpyridino-18-crown-6 with (R)- and (S)-[-(1-naphthyl)ethyl]ammonium perchlorate. This finding is supported by the¹H NOESY NMR spectral technique, greater chemical shift changes of aromatic protons in both host and guest molecules upon complexation, and by molecular mechanics calculations. Because of the flexibility of the ligand, the tripod hydrogen bonding causes¹³C relaxation times of all periphery carbons to decrease without significant selectivity. Rotational energy barrier calculations of the methyl groups of the complexed ligand also show that the (S, S)-host-(R)-guest is the more stable complex.