Cycloaddition of anhydro bases of heterocyclic cations.

A new method of spiro-ring formation by the reaction of s-tetrazines with anhydro bases was described. The prototropic transitions were detected in the pyridazine fragments of the resulting spirocyclic compounds. The heterocycles of the anhydro bases are converted to cyclic ketones as a result of the breaking of the spiro junction in the acidic hydrolysis of the spirohetarenes. The regioselectivity of the cycloaddition was established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1244–1249, September, 1990.     

Synthesis and Reactions of 1,4‐Anhydrogalactopyranose and 1,4‐Anhydroarabinose – Steric and Electronic Limitations

Scope and limitations of 1,4‐anhydro sugars as precursors of glycofuranosyl building blocks are described. The experiments revealed that the choice of the substituents is very important for an efficient preparation as well as a successful ring‐opening reaction of 1,4‐anhydro sugars. DFT Calculations suggest that selective protonation of 1,4‐anhydro sugars is the key to the selective ring opening in order to afford only furanosides.     

O,O-dialkylphosphoroselenoic acids as functionalising reagents of monosaccharides—III: A novel synthesis of unsaturated sugars by eoxygenation of sugar epoxides with dialkylphosphoroselenoic acids

Sugar epoxides are transformed in almost quantitative yields, under mild reaction conditions, into their corresponding unsaturated monosaccharides by reaction with O,O-dialkylphosphoroselenoic acids salts. A mechanism involving the formation of a penta-coordinate phosphorus intermediate is proposed.The deoxygenation was performed with the following sugar epoxides: 5,6 - anhydro -1,2 - O - isopropylidene - α - D - glucofuranose (1), 5,6 - anhydro - 1,2 - O - cyclohexylidene - α - D - glucofuranose (2), methyl - 2,3 - anhydro - 4, 6 - O - benzylidene - α - D - allopyranoside (3), methyl - 2,3 - anhydro - 4,6 - O - benzylidene - α - D - mannopyranoside (4) and 3,4,6 - tri - O - acetyl - 1,2 - anhydro - α - D - glucopyranose (Brigl's anhydride) (5).     

Anhydro bases of the pyridine series (review)

Methods for the preparation of anhydro bases of the pyridine series by deprotonation of the corresponding quaternary salts under the influence of bases, as well as by the direct reaction of quaternary pyridinium or halopyridinium salts with CH acids in the presence of bases, are examined. The reactions of anhydro bases with various reagents (alkyl cations, acylium cations, the proton, aldehydes, isothiocyanates, carbon disulfide, the hydroxide ion, etc.), which constitute evidence for their high reactivities, are examined. The participation of anhydro bases as intermediates in many reactions intended for the preparation of new heterocyclic systems is demonstrated.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.3, pp. 291–311, March, 1982.     

Mass spectrometry of polymethine dyes

The mass spectra of some unsubstituted (in the heteroresidues and polymethine chain) thiacarbo- and polycarbocyanines were investigated. It was ascertained that the first act of disintegration of the dye molecules is splitting out of an alkyl halide ion to give an anhydro base ion. Some regularities between the structure of the dyes and the fragmentation of the anhydro ions obtained from them are exposed. The peculiarities of the dissociative ionization of the dye molecules as the polymethine chain is lengthened are shown.     

Synthesis of a new 2‐amino‐glycan,poly‐(1→6)‐α‐D‐mannosamine,by ring‐opening polymerization of 1,6‐anhydro‐mannosamine derivatives

A stereoregular 2‐amino‐glycan composed of a mannosamine residue was prepared by ring‐opening polymerization of anhydro sugars. Two different monomers, 1,6‐anhydro‐2‐azido‐mannose derivative ( 3 ) and 1,6‐anhydro‐2‐(N, N‐dibenzylamino)‐mannose derivative ( 6 ), were synthesized and polymerized. Although 3 gave merely oligomers, 6 was promptly polymerized into high polymers of the number‐average molecular weight (M_n) of 2.3 × 10⁴ to 2.9 × 10⁴ with 1,6‐α stereoregularity. The differences of polymerizability of 3 and 6 from those of the corresponding glucose homologs were discussed. It was found that an N‐benzyl group is exceedingly suitable for protecting an amino group in the polymerization of anhydro sugars of a mannosamine type. The simultaneous removal of O‐ and N‐benzyl groups of the resulting polymers was achieved by using sodium in liquid ammonia to produce the first 2‐amino‐glycan, poly‐(1→6)‐α‐D ‐mannosamine, having high molecular weight through ring‐opening polymerization of anhydro sugars.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Investigation of the influence of a sulfur atom on the mobility of the hydrogen atoms in a methylene group of some heterocyclic compounds

The action of dicyclohexylcaibodiimide on 2-benzimidazolylthioacetic,-(2-benzimidazolylthio)propionic,-(2-benzimidazolyl)propionic and 2-benzimidazolylacetic acids has given the anhydro derivatives of these acids. It has been shown that the hydrogen atoms in the methylene group of anhydro-2-benzimidazolylthioacetic acid have the highest mobility.     

Mass spectrometry of onium compounds—VI: Pyrimidinium oxides

The 5-methyldihydrothiazolo (3,2-c) pyrimidinium cation is evaporated as the corresponding anhydro base. In competition with anhydro base formation the 8-ethoxy derivative eliminates ethyl bromide to give the corresponding betaine. The latter appears to be electronically rearranged and evaporated as a covalent valence isomer. The 3-carboxy derivative investigated suffered decarboxylation and ring opening to a vinyl thione. In the absence of a pyrimidyl methyl group the thiazolo ring was attacked by the anion. The electronically induced fragmentations are discussed and used to deduce the structures of the pyrolytic products.     

Cycloaddition of anhydro bases of heterocyclic cations. 2. Synthesis of spirocyclic and carcass structures in the reaction of s-tetrazines with the anhydro base of a quaternary lepidinium salt

The anhydro base of an N-methyllepidinium salt reacts with s-tetrazines to give spiro hetarenes with 4,5- and 1,4-dihydropyridazine structures. The regioselectivity of the cycloaddition was established. In addition to spiro annelation, intramolecular cyclization to give compounds with a carcass structure, for which x-ray diffraction analysis was carried out, occurs when s-tetrazines with -pyridyl substituents are used.See [1] for Communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1545–1551, November, 1991.     

Synthesis and reactions of 2-(4-pyridyl)indole anhydro bases

The corresponding anhydro bases are formed from quaternary salts of 2-(4--pyridyl)indole under the influence of a methanol solution of alkali. The 2-(4-pyridyl)indole cation and 1H-4-(2-indolenylidene)-1,4-dihydropyridine were subjected to quantum-chemical calculation, and the possibility of electrophilic substitution of the anhydro bases in the position of indole was predicted on the basis of the results of the calculations. Thus, the reaction of the anhydro bases with acetyl nitrate and a solution of bromine in acetic acid leads to quaternary salts with a substituent in the position of the indole ring, which are reconverted to anhydro bases under the influence of alkali with retention of the substituent in the position. When the anhydro bases are refluxed in nitromethane and cyanoacetic and malonic esters in the presence of triethylamine, they form the corresponding adducts, which give the starting compounds under the influence of alkali, whereas upon reaction with methyl iodide in ethanol they give quaternary salts. All of these chemical transformations were confirmed by the IR, UV, PMR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 52–58, January, 1982.     

Mass spectral studies on mesoionic imidazo [1,2-a] pyrid-2 and -3-one derivatives

The mass spectral fragmentation patterns for 1-substituted derivatives of anhydro (3-chloroacetyl-2-hydroxyimidazo[1,2-a]pyridinium hydroxide) (Ia to Ie) and 2-acyl substituted derivatives of anhydro(1-benzyl-3-hydroxyimidazo[1,2-a]pyridinium hydroxide) (IIa and IIb) are reported. In all cases the mass spectra may be interpreted on the basis of initial cleavage of the ‘carbonyl-heteroatom’ bond of the mesoionic system, followed by fragmentation.     

Complex Formation and Flower Colors

The pigment of the blue cornflower, protocyanin, is a complex of high molecular weight. Iron(III) and aluminum ions combine with the anhydro base of the cyanin to form deep-blue complexes, which are stable in the physiological pH range. Complexes of this type also have been synthesized. Alkali metal salts play no part in blue flower pigments. Formation of blue complexes can be prevented by sequestration of the metal ions with stronger complexing agents, e.g. flavonols. The variation of flower colors can be explained to a large extent on the basis of the complex formation of anthocyanins. In delphinidin glycosides, the color base or anhydro base is stable even in slightly acidic media.     

Ring‐opening polymerization of benzylated 1,6‐anhydro‐β‐D‐lactose and specific biological activities of sulfated (1→6)‐α‐D‐lactopyranans

A new anhydro disaccharide monomer, 1,6‐anhydro‐2,3‐di‐o‐benzyl‐4‐o‐(2′,3′,4′,6′‐tetra‐o‐benzyl‐β‐D ‐galactopyranosyl)‐β‐D ‐glucopyranose (benzylated 1,6‐anhydro lactose (LSHBE)), was synthesized from D ‐lactose to investigate the polymerizability and biological activities of the resulting branched polysaccharides. The ring‐opening polymerization of LSHBE was carried out with phosphorus pentafluoride as a catalyst under high vacuum to give a stereoregular benzylated (1 → 6)‐α‐D ‐lactopyranan. The molecular weights of poly(LSHBE)s increased with an increase in the amount of CH₂Cl₂ solvent, and polymerization temperatures were affected in both molecular weights and yields of the polymers. The copolymerization of LSHBE with benzylated 1,6‐anhydro‐β‐D ‐glucopyranose (LGTBE) gave the corresponding copolysacchrides having different proportions of lactose and glucose units in good yields. After debenzylation to recover hydroxyl groups and then sulfation, sulfated homopoly(lactose)s and copoly(lactose and glucose)s were obtained. Sulfated homopoly(lactose)s had moderate anti‐HIV (EC₅₀ = 5.9 and 1.3 μg/mL) and blood anticoagulant activities (AA = 18 and 13 unit/mg), respectively. Sulfated copoly(lactose and glucose) having 15 mol % lactose units gave high anti‐HIV and blood anticoagulant activities of 0.3 μg/mL and 54 unit/mg, respectively. These biological results suggest that the distance between branched units on the main chain plays an important role in the anti‐HIV and blood anticoagulant activities. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 913–924, 2009     

Synthesis of Tri-O-acetyl-d-allal from Levoglucosenone

Tri-O-acetyl-d-allal has been enantiospecifically synthesized in six steps from levoglucosenone in 55% overall yield. A key step in the synthesis is the anhydro bridge ring-opening with concomitant formation of a 1,3-oxathiolane-2-thione ring.     

Structure of the anhydro base of the 1-phenyl-3-acetyllepidinium cation

The anhydro base of the 1-phenyl-3-acetyllepidinium cation, which is characterized by increased stability, was isolated, and a structure was proposed for it.Translated from Khimiya Geterotsiklicheskikh Soedinenti, No. 3, pp. 359–361, March, 1972.     

Reactions of lycoctonine alkaloids with acetic anhydride and p-toluenesulfonic acid

The reactions of alkaloids having a 7,8-diol system — lycoctonine, browniine, and dihydromonticoline — with acetic anhydride and p-toluenesulfonic acid have been studied. The optimum conditions for this reaction, leading to anhydro compounds, have been found.     

C5–C10 Directly Bonded Tetrodotoxin Analogues: Possible Biosynthetic Precursors of Tetrodotoxin From Newts

The identification of novel tetrodotoxin (TTX, 1 ) analogues would significantly contribute to the elucidation of its biosynthetic pathway. In this study, the first C5–C10 directly bonded TTX analogues, 4,9‐anhydro‐10‐hemiketal‐5‐deoxyTTX ( 2 ) and 4,9‐anhydro‐8‐epi‐10‐hemiketal‐5,6,11‐trideoxyTTX ( 3 ), were found in the newt Cynops ensicauda popei by using a screening method involving HILIC‐LC–MS/MS focused on the fragment ions of TTX analogues, and their structures were elucidated by spectroscopic methods. Compound 2 was detected in a wide range of newt species, and the 2 and TTX contents of 22 newt specimens were correlated (r_s=0.88). Based on these results and its structural features, 2 was predicted to serve as a precursor of TTX that would be directly converted into 4,9‐anhydroTTX ( 4 ) by Baeyer–Villiger‐like oxidation or via 4,9‐anhydro‐5‐deoxyTTX formed by cleavage of the C5–C10 bond. The bicyclic carbon skeletons of 2 and 3 suggested a possible monoterpene origin for TTX.     

Cycloaddition reactions of the anhydro-4-hydroxythiazolium hydroxide system with dimethyl maleate and dimethyl fumarate : X-ray determination of the exo structure of the cycloadducts

The relative configuration of the carbons bearing the ester groups in the cycloadducts of anhydro - 4- hydroxythiazolium hydroxides with dimethyl maleate and dimethylfumarate is revised in the light of an X-ray crystallographic analysis. Steric effects are considered to account for the preferred exo approach of the dipole and the dipoiarophile.     

Synthesis of compounds of interest in proton transfer spectroscopy

A new series of compounds has been prepared for use in proton transfer spectroscopy. The complexes 6a-6d have been converted into the fully characterised perchlorates 7a-7d and the corresponding anhydro bases 8a-8d.