scholarly journals A new synthetic access to 2-N-(glycosyl)thiosemicarbazides from 3-N-(glycosyl)oxadiazolinethiones and the regioselectivity of the glycosylation of their oxadiazolinethione precursors

2013 ◽  
Vol 9 ◽  
pp. 135-146 ◽  
Author(s):  
El Sayed H El Ashry ◽  
El Sayed H El Tamany ◽  
Mohy El Din Abdel Fattah ◽  
Mohamed R E Aly ◽  
Ahmed T A Boraei ◽  
...  
Keyword(s):  
Ring Opening ◽  
Ion Pair ◽  
Aqueous Methanol ◽  
Reaction Conditions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Basic Alumina ◽  
Minor Degree

Glycosylations of 5-(1H-indol-2-yl)-1,3,4-oxadiazoline-2(3H)-thione delivered various degrees of S- and/or N-glycosides depending on the reaction conditions. S-Glycosides were obtained regiospecifically by grinding oxadiazolinethiones with acylated α-D-glycosyl halides in basic alumina, whereas 3-N-(glycosyl)oxadiazolinethiones were selectively obtained by reaction with HgCl2 followed by heating the resultant chloromercuric salt with α-D-glycosyl halides in toluene under reflux. On using Et3N or K2CO3 as a base, mixtures of S- (major degree) and N-glycosides (minor degree) were obtained. Pure 3-N-(glycosyl)oxadiazolinethiones can also be selectively obtained from glycosylsulfanyloxadiazoles by the thermal S→N migration of the glycosyl moiety, which is proposed to occur by a tight-ion-pair mechanism. Thermal S→N migration of the glycosyl moiety can be used for purification of mixtures of S- or N-glycosides to obtain the pure N-glycosides. The aminolysis of the respective S- or N-glycosides with ammonia in aqueous methanol served as further confirmation of their structures. While in S-glycosides the glycosyl moiety was cleaved off again, 3-N-(glycosyl)oxadiazolinethiones showed a ring opening of the oxadiazoline ring (without affecting the glycosyl moiety) to give N-(glycosyl)thiosemicarbazides. Herewith, a new synthetic access to one of the four classes of glycosylthiosemicarbazides was found. The ultimate confirmation of new structures was achieved by X-ray crystallography. Finally, action of ammonia on benzylated 3-N-(galactosyl)oxadiazolinethione unexpectedly yielded 3-N-(galactosyl)triazolinethione. This represents a new path to the conversion of glycosyloxadiazolinethiones to new glycosyltriazolinethione nucleosides, which was until now unknown.

scholarly journals Rational synthesis of an atomically precise carboncone under mild conditions

2019 ◽  
Vol 5 (8) ◽  
pp. eaaw0982 ◽  
Author(s):  
Zheng-Zhong Zhu ◽  
Zuo-Chang Chen ◽  
Yang-Rong Yao ◽  
Cun-Hao Cui ◽  
Shu-Hui Li ◽  
...  
Keyword(s):  
Apex Angle ◽  
Facile Synthesis ◽  
Reaction Conditions ◽  
X Ray ◽  
Carbon Allotropes ◽  
X Ray Crystallography ◽  
Mild Conditions ◽  
Research Opportunity ◽  
Insight Into ◽  
Structural Strain

Carboncones, a special family of all-carbon allotropes, are predicted to have unique properties that distinguish them from fullerenes, carbon nanotubes, and graphenes. Owing to the absence of methods to synthesize atomically well-defined carboncones, however, experimental insight into the nature of pure carboncones has been inaccessible. Herein, we describe a facile synthesis of an atomically well-defined carboncone[1,2] (C70H20) and its soluble penta-mesityl derivative. Identified by x-ray crystallography, the carbon skeleton is a carboncone with the largest possible apex angle. Much of the structural strain is overcome in the final step of converting the bowl-shaped precursor into the rigid carboncone under mild reaction conditions. This work provides a research opportunity for investigations of atomically precise single-layered carboncones having even higher cone walls and/or smaller apex angles.

scholarly journals Übergangsmetall-Carben-Komplexe, CXXXIV [1]. Synthese neuer Mono- und Biscarben-Komplexe der VI. Nebengruppe; Röntgenstruktur des ersten Bis[amino(alkoxy)carben]-Komplexes / Transition Metal Carbene Complexes, CXXXIV [1]. Synthesis of New Mono- and Bis-Carbene Complexes of Group VIb Elements; Structure of the First Bis[amino(alkoxy)carbene]-Complex

1984 ◽  
Vol 39 (5) ◽  
pp. 668-674 ◽  
Author(s):  
Ernst Otto Fischer ◽  
Rudolf Reitmeier ◽  
Klaus Ackermann
Keyword(s):  
Molecular Structure ◽  
Transition Metal ◽  
Spectroscopic Data ◽  
The Novel ◽  
Nucleophilic Agent ◽  
Reaction Conditions ◽  
Carbene Complexes ◽  
X Ray ◽  
X Ray Crystallography ◽  
New Compounds

The hexacarbonyl compounds of chromium, molybdenum and tungsten react with the highly nucleophilic agent Li NiPr2 and in a subsequent alkylation with (Et3O)BF4 to give the carbene complexes (CO)5M[C(N′Pr2)OEt] (1, 3, 4). In case of W(CO)6 and Mo(CO)6 the novel biscarbene complexes cis(CO)4M[C(NiPr2)OEt]2 (2, 5) are additionally obtained. Reaction conditions, properties and spectroscopic data of the new compounds are reported. The molecular structure of cis(CO)4W[C(NiPr2)OEt]2 (4) was determined by X-ray crystallography

Structural studies of some 1-polymethyleneimino-2,4-dinitrobenzenesand related compounds; crystal structure of 1-(cis-2′,6′-dimethylpiperidin-1′-yl)-2,4-dinitrobenzene

2000 ◽  
Vol 53 (8) ◽  
pp. 715 ◽  
Author(s):  
Maureen F. Mackay ◽  
Douglas J. Gale ◽  
John F. K. Wilshire
Keyword(s):  
Crystal Structure ◽  
Phenyl Ring ◽  
Ring Opening ◽  
Boat Conformation ◽  
Structural Studies ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Mean ◽  
Related Compounds ◽  
Solid State Conformation

The ultraviolet and 1H n.m.r. spectra of some 1-polymethyleneimino-2,4-dinitrobenzenes and related compounds are discussed. The effect of trifluoroacetic acid on these spectra was also investigated; with 1-azetidinyl-2,4-dinitrobenzene, acid-catalysed ring opening was observed. The solid-state conformation of 1-(cis-2′,6′-dimethylpiperidin-1′-yl)-2,4-dinitrobenzene has been defined by single-crystal X-ray crystallography. Triclinic crystals belong to the space group P–1 with a 8.165(1), b 7.865(1), c 11.148(1) Å, α 95.23(1), β 106.00(1), γ 92.63(1)˚ and Z 2. The structure was refined to a final R of 0.048 for the 2222 observed data. In the crystal, the phenyl ring adopts a slight boat conformation, while the amino and o-nitro groups are significantly twisted from the mean plane of the ring.

scholarly journals Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

2019 ◽  
Vol 15 ◽  
pp. 79-88 ◽  
Author(s):  
Sibylle Frei ◽  
Adam K Katolik ◽  
Christian J Leumann
Keyword(s):  
Building Block ◽  
Ring Opening ◽  
Structural Investigation ◽  
Cyclopropane Ring ◽  
Cd Spectroscopy ◽  
Rnase H ◽  
Biophysical Properties ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cleavage Assay

Here we present the synthesis, the biophysical properties, and the RNase H profile of 6’-difluorinated [4.3.0]bicyclo-DNA (6’-diF-bc4,3-DNA). The difluorinated thymidine phosphoramidite building block was synthesized starting from an already known gem-difluorinated tricyclic glycal. This tricyclic siloxydifluorocyclopropane was converted into the [4.3.0]bicyclic nucleoside via cyclopropane ring-opening through the addition of an electrophilic iodine during the nucleosidation step followed by reduction. The gem-difluorinated bicyclic nucleoside was then converted into the corresponding phosphoramidite building block which was incorporated into oligonucleotides. Thermal denaturation experiments of these oligonucleotides hybridized to complementary DNA or RNA disclosed a significant destabilization of both duplex types (ΔT m/mod = −1.6 to −5.5 °C). However, in the DNA/RNA hybrid the amount of destabilization could be reduced by multiple insertions of the modified unit. In addition, CD spectroscopy of the oligonucleotides hybridized to RNA showed a similar structure than the natural DNA/RNA duplex. Furthermore, since the structural investigation on the nucleoside level by X-ray crystallography and ab initio calculations pointed to a furanose conformation in the southern region, a RNase H cleavage assay was conducted. This experiment revealed that the oligonucleotide containing five modified units was able to elicit the RNase H-mediated cleavage of the complementary RNA strand.

scholarly journals Synthesis and Characterization of Various Amino Acid Derived Thiohydantoins

Proceedings ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 37
Author(s):  
Petar Stanić ◽  
Marija Živković ◽  
Biljana Šmit
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Allyl Isothiocyanate ◽  
Structural Diversity ◽  
Biologically Active ◽  
Reaction Conditions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Sulfur Containing

Hydantoins and their sulfur containing analogues, thiohydantoins, are cyclic ureides that have attracted huge attention ever since their discovery. Most of them are biologically active compounds and several points of structural diversity have made them very synthetically attractive. Although substituents can be introduced to the hydantoin nucleus, most substituted hydantoins are synthesized from substrates already containing these groups, while forming the hydantoin nucleus. This is a common route to the synthesis of hydantoins and one of them is employed in this study. A series of 3-allyl-2-thiohydantoins is synthesized from various α-amino acids in a reaction with allyl isothiocyanate. The substitution of the acquired thiohydantoin depends on the structure of the starting α-amino acid. The residual group of the α-amino acid becomes the substituent at the C5-position, while N-monosubstituted amino acids give rise to a substituent in the N1-position. The reaction is carried out in a two-step process and the reaction conditions generally depend on the nature of the amino acid itself. All thiohydantoins are obtained in a good yield and fully characterized by NMR and IR spectroscopy, as well as X-ray crystallography.

The reaction of chloro(triphenylphosphine)gold(I) with 1-methylthymine

1987 ◽  
Vol 65 (7) ◽  
pp. 1568-1575 ◽  
Author(s):  
R. Faggiani ◽  
H. E. Howard-Lock ◽  
C. J. L. Lock ◽  
M. A. Turner
Keyword(s):  
Aqueous Methanol ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Cell Dimensions ◽  
Cell Data ◽  
Unit Cell Data ◽  
Related Compounds ◽  
C Nmr

1-Methylthyminato-N3-triphenylphosphinegold(I) was prepared by reacting chloro(triphenylphosphine)gold(I) with 1-methylthymine in aqueous methanol at pH 11. The product was examined by X-ray crystallography and was found to have the orthorhombic space group C2221 (no. 20) with cell dimensions a = 12.760(7) Å, b = 11.530(2) Å, c = 31.893(5) Å, and eight formula units in the unit cell. Data were collected with use of MoKα radiation and a Syntex P21, diffractometer. The crystal structure was determined by standard methods and refined to R = 0.112 and Rw = 0.076 on the basis of 4760 unique reflections. Bond lengths and bond angles are normal. Packing in the crystal lattice is dominated by the triphenylphosphine rings which arrange roughly as blades of a propellor and are the source of the crystal's chirality. The title and related compounds were also examined by 1H nmr, 13C nmr, and vibrational spectroscopy.

scholarly journals Efficient Preparation of Potassium Arylmethylene-4-(1H-Pyrazol-5-ol)-4′-(1H-Pyrazol-5-Olate) Derivatives via a Four-Component Reaction

2018 ◽  
Vol 42 (6) ◽  
pp. 313-316
Author(s):  
Ting Wang ◽  
Yang Yu ◽  
Xushun Qing ◽  
Chenlu Dai ◽  
Cunde Wang
Keyword(s):  
Potassium Carbonate ◽  
Reaction Conditions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Broad Scope ◽  
Substituted Benzaldehydes ◽  
High Yields ◽  
Operational Simplicity

A four-component reaction was investigated to prepare potassium arylmethylene-4-(1 H-pyrazol-5-ol)-4′-(1 H-pyrazol-5-olate) derivatives from dialkyl but-2-ynedioates, phenylhydrazine, substituted benzaldehydes and potassium carbonate without any catalyst or promoter. The structure of a typical product was confirmed by X-ray crystallography. The advantages of the present methodology are efficiency, broad scope, operational simplicity, high yields and mild reaction conditions.

Synthesis, Characterization and Reactivity of a Diorganotin Thiocarboxylate: Dimethyl(thioacetato)-tin(IV) Chloride and its Reactions with Nucleophiles Exhibiting Desulfurization

2009 ◽  
Vol 64 (1) ◽  
pp. 116-122 ◽  
Author(s):  
Neetu Singh ◽  
Subrato Bhattacharya ◽  
Heinrich Nöth ◽  
Peter Mayer
Keyword(s):  
Ftir Spectroscopy ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Thioacetic Acid ◽  
Reaction Conditions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Tin Chloride ◽  
Reactions With Nucleophiles

Dimethyl(thioacetato)tin chloride (1) was synthesized by the reaction of dimethyltin dichloride with thioacetic acid in the presence of triethylamine. Compound 1 was subjected to hydrolysis under different reaction conditions in order to obtain sulfido/hydrosulfidotin compounds. Except for one case where the product was hexamethyl-1,3,5-trithia-2,4,6-tristannacyclohexane, (Me2SnS)3 (4), all other reactions led to desulfurization, and the products obtained were organostannoxane compounds, dinuclear tetramethyl-oxo-dichloroditin, {Me2SnCl2.Me2SnO}2 (2), and tetraacetatodioxotetra( dimethyltin), (Me2Sn)4O2(O2CMe)4 (3). These complexes have been characterized by 1H, 13C, 119Sn NMR and FTIR spectroscopy, and compounds 2 - 4 also by X-ray crystallography. Density functional calculations were performed to explain the structure and reactivity of the compounds.

scholarly journals Preparation of Pincer Hafnium Complexes for Olefin Polymerization

Molecules ◽  
2019 ◽  
Vol 24 (9) ◽  
pp. 1676 ◽  
Author(s):  
Su Jin Kwon ◽  
Jun Won Baek ◽  
Hyun Ju Lee ◽  
Tae Jin Kim ◽  
Ji Yeon Ryu ◽  
...  
Keyword(s):  
Olefin Polymerization ◽  
Ion Pair ◽  
Metallocene Catalysts ◽  
X Ray ◽  
X Ray Crystallography ◽  
Pyridine Moiety ◽  
No Formation ◽  
Type Complex ◽  
Ligand Precursors

Pincer-type [Cnaphthyl, Npyridine, Namido]HfMe2 complex is a flagship among the post-metallocene catalysts. In this work, various pincer-type Hf-complexes were prepared for olefin polymerization. Pincer-type [Namido, Npyridine, Namido]HfMe2 complexes were prepared by reacting in situ generated HfMe4 with the corresponding ligand precursors, and the structure of a complex bearing 2,6-Et2C6H3Namido moieties was confirmed by X-ray crystallography. When the ligand precursors of [(CH3)R2Si-C5H3N-C(H)PhN(H)Ar (R = Me or Ph, Ar = 2,6-diisopropylphenyl) were treated with in situ generated HfMe4, pincer-type [Csilylmethyl, Npyridine, Namido]HfMe2 complexes were afforded by formation of Hf-CH2Si bond. Pincer-type [Cnaphthyl, Sthiophene, Namido]HfMe2 complex, where the pyridine moiety in the flagship catalyst was replaced with a thiophene unit, was not generated when the corresponding ligand precursor was treated with HfMe4. Instead, the [Sthiophene, Namido]HfMe3-type complex was obtained with no formation of the Hf-Cnaphthyl bond. A series of pincer-type [Cnaphthyl, Npyridine, Nalkylamido]HfMe2 complexes was prepared where the arylamido moiety in the flagship catalyst was replaced with alkylamido moieties (alkyl = iPr, cyclohexyl, tBu, adamantyl). Structures of the complexes bearing isopropylamido and adamantylamido moieties were confirmed by X-ray crystallography. Most of the complexes cleanly generated the desired ion-pair complexes when treated with an equivalent amount of [(C18H37)2N(H)Me]+[B(C6F5)4]−, which showed negligible activity in olefin polymerization. Some complexes bearing bulky substituents showed moderate activities, even though the desired ion-pair complexes were not cleanly afforded.

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