Dibenzyl phosphorofluoridate,a new phosphorylating agent

The first synthesis of dibenzyl phosphorofluoridate and its utility as a phosphorylating agent are described.     

S-4-methylphenyl-o,o-bis[1-benzotriazolyl] phosphorothioate: a versatile phosphorylating agent

The phosphorylating agent obtained by treatment of S-4-methylphenyl phosphorodichloridothioate with 1-hydroxybenzotriazole can not only be applied for the introduction of polyphosphate functions at the terminal ends of nucleic acids, but also for the formation of 3′-5′-phosphotriester linkages.     

The p-nitrophenylethyl (NPE) group: A versatile new blocking group for phosphate and aglycone protection in nucleosides and nucleotides

The syntheses of new monomer building blocks for oligonucleotide synthesis via the phosphotriester approach containing the p-nitrophenylethyl group for phosphate and aglycone protection are described. Blocking of the amide function in guanosines at O⁶ can be achieved by the Mitsunobu reaction forming the corresponding O⁶-p-nitrophenylethyl derivatives (4,5,10). Sugar-protected thymidine (16) and uridine (17) have been alkylated at O⁴ in an S_N1-type reaction by p-nitrophenylethyl iodide-silver carbonate in benzene to form the O⁴-p-nitrophenylethyl derivatives (18,19). Protection of the amino group in 2'-deoxycytidine (25) and cytidine (26) can be performed directly by 1-(p-nitrophenylethoxycarbonyl)-benzotriazole in DMF to obtain the corresponding carbamates (27,28) as a new type of N⁴-acylated cytidine derivative. p Nitrophenylethoxycarbonylation of the amino group in 2'-deoxyadenosine (33) and adenosine (34) requires previous sugar protection by acyl or silyl groups and can then be achieved by p-nitrophenylethyl chloroformate or better by 1-methyl-3-p-nitrophenylethoxycarbonylimidazolium chloride to form N⁶-p-nitrophenylethoxycarbonyladenosines (38,39,40,42). The various /-nitrophenylethyl blocking groups are stable under mild hydrolytic conditions (e.g. ammonia and triethylamine) but can be cleaved selectively by DBU or DBN in aprotic solvents. 5'-O-Monomethoxytritylation (12,29,43) as well as phosphorylations at the 3'-OH group can be effected to give the corresponding 3'-(2,5-dichlorophenyl,/-nitrophenylethyl)-phosphotriesters (13,22,30,44) also in high yields. Oximate cleavage of the latter compounds to the phosphodiesters (14,24,32,46) and detritylation to the 5'-unblocked phosphotriesters (15,23,31,45) do not affect the aglycone protecting groups, thereby demonstrating their general versatility. The newly synthesized compounds have been characterized on the basis of their elementary analyses (C, H, N), and UV- and ¹H-NMR-spectra.     

Symm-bis(p-nitrophenylethyl)ethylene-1, 2-diphosphonate

Conclusions Symm-bis(p-nitrophenylethyl)ethylene-1,2-diphosphonate, which is a bifunctional phosphorylating agent, was produced.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1115–1116, June, 1966.     

Bis- and tetrakis(organosilyl) decatungstosilicate,

The high propensity of organosilanes towards polycondensation and reaction with nucleophilic moieties has facilitated the formation of new organic-inorganic hybrids based on the lacunary divacant heteropolyanion [gamma-SiW10O36]8-. Depending on the experimental conditions two different types of derivatives were obtained with the general formula [gamma-SiW10O36(RSi)2O]4- (1) (>90% yield) and [gamma-SiW10O36(RSiO)4]4- (2) (>85% yield) (R = H (1a, 2a), vinyl (1b), -C3H6OC(O)C-(Me)=CH2 (1c, 2c), phenyl (1d, 2d)). The structures of the hybrid anions have been inferred from spectroscopic data, in particular from multinuclear (29Si and 183W) NMR solution studies and from MALDI-TOF mass spectrometry. Both species correspond to the grafting of an oxo-bridged siloxane unit onto the surface of the lacunary polyoxoanion.     

Bis-(trialkylsilyl) phosphonates

Summary Methods of synthesis of the previously unknown bis-(trialkylsilyil) phosphonates were developed on the basis of reaction of phosphorous acid with trialkylchlorosilanes or trialkylalkoxysilanes. Their Raman spectra were studied.     

Bis-η5-cyclopentadienyl and Bis-η5-methylcyclopentadienylN,N-dialkyldithiocarbamato(chloro)titanium(IV) compounds

Summary Titanium(IV)N,N-dialkyldithiocarbamates of the type ⁵-Cp₂Ti (S₂CNR₂)Cl and (⁵-MeCp)₂Ti(S₂CNR₂)Cl (R = Me, Et and i-Pr) have been prepared by the reaction of di--cyclopentadienyldichlorotitanium(IV) and bis-n-methylcyclopentadienyldichlorotitanium(IV) with sodium salts of dithiocarbamic acids in refluxing dichloromethane. Molecular weight, conductance and i.r. studies show these complexes to be monomeric nonelectrolytes in which the dithiocarbamate ligands are bidentate. Therefore, pentacoordination may be assigned to titanium(IV) atom in all six complexes. Electronic and proton n.m.r. studies spectra have also been recorded for the complexes.     

Phosphoryl tris-triazole - a new phosphorylating reagent

Phosphoryl tris-triazole, a new phosphorylating reagent obtained from POCl₃ and 1,2,4-triazole, was found to be very useful for the preparation of nucleoside 3′-phosphotriesters bearing various alkyl phosphate protective groups.     

Mono-, Bis- und Tris(trimethylsilyl)hydroxylamin

Ohne ZusammenfassungMit 1 Abbildung77. Mitt.:U. Wannagat undM. Schulze, Z. Chem.8, 255 (1968).Vorläufige Mitt.:U. Wannagat, Angew. Chem.78, 648 (1966).Auszugsweise vorgetragen auf dem 155th National Meeting der American Chemical Society, San Francisco, April 1968.Sonderdrucke überU. W., D-33 Braunschweig, Pockelsstr. 4, Inst. für Anorg. Chem. der Techn. Universität.Mit Auszügen aus der DissertationO. Smrekar, Techn. Hochschule Graz 1969.     

Bis(2-thienyl)silanes: new, versatile precursors to arylsilanediols

Silanediols have been shown to be effective bioisosteres for the hydrated carbonyl group. Current methods for the formation of silanediols place a number of constraints on how and where this functionality may be used. A range of arylsilanes that would allow both the formation of arylsilanediols and that are also compatible with multi-step synthetic routes, have been investigated as possible precursors to silanediols. Through this study bis(2-furyl)silanes and, in particular, bis(2-thienyl)silanes have been identified as practical precursors to arylsilanediols.     

ZnO: a versatile agent for benzylic oxidations

Zinc oxide catalyzed oxidation of various alkylbenzenes, naphthalene and 1,2,3,4-tetrahydronaphthalene in air using microwave irradiation or conventional heating in the presence of N,N-dimethylformamide is described.     

二苄烯肼的氯化反应

二苄烯肼经氯化反应合成了二(α-氯-苄烯)肼(1)和苄烯苯甲酰肼(2)。其结构经1H NMR,IR,MS和X-射线单晶衍射表征。1为单斜晶系,空间群为Pn,a=11.468(9),b=7.518(4),c=14.929(10),β=99.23(6)°,V=1270.5(15)3,Z=4,Dc=1.449 g.cm-3,F(000)=568,λ(Mo Kα)=0.71073,μ=0.492 mm-1。2为三斜晶系,空间群为Pna21,a=8.7848(3),b=10.4556(3),c=13.1238(4),α=90°,β=90°,γ=90°,V=1205.43(7)3,Z=4,Dc=1.236 g.cm-3,F(000)=472,μ(Mo Kα)=0.763mm-1(0.71073)。2中存在分子间和分子内的氢键。1和2的分子结构表明:二苄烯肼氯化作用是分步进行的;水的存在影响二苄烯肼的氯化作用;反应过程中第一步的产物不稳定,在水存在下,发生水解重排反应生成2。讨论了有关反应机理。     

Structural, Spectroscopic, and Thermal Behaviour of Bis-(thiosaccharinate)-aqua-cadmium(II)

Summary.  The crystal structure of the title complex, [Cd(tsac)₂(H₂O)], has been determined by single crystal X-ray diffraction methods. It crystallizes in the monoclinic space group C2/c (a = 12.236(3), b = 8.919(3), c = 16.655(3) ?, β = 96.18(2)°, Z = 4). The molecular structure was solved from 1705 independent reflections with I > σ(I) and refined to R ₁ = 0.0489. Infrared and Raman spectra of the complex were recorded and are briefly discussed. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis. Received December 18, 2000. Accepted February 19, 2001     

Synthesis and characterization of a new lanthanide based MRI contrast agent,potential and versatile tracer for multimodal imaging

In the present work a modular pathway towards the synthesis of a new versatile MRI contrast agent is reported and its physico-chemical properties are described. Two different functional groups were attached on two arms of the gadolinium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) in order to get a platform able to bind one probe designed to target specific biological marker and a fluorescent molecule likely to be used for optical imaging. The nuclear magnetic relaxation dispersion (NMRD) profile, the oxygen-17 relaxometric NMR study and stability assessment versus transmetalation of the Gd-complex show that this new contrast agent has a relaxivity and transmetalation stability similar to Gd–DOTA.     

Birch reduction of (-)-ephedrine. Formation of a new, versatile intermediate for organic synthesis

The reduction of (-)-ephedrine by lithium in liquid ammonia resulted in the formation of S-1-(1,4-cyclohexadien-1-yl)-N-methyl-2-propanamine. In addition to the reduction of the aromatic ring, the hydroxy group was reduced as well. The resulting 1,4-cyclohexadienyl group is a potentially versatile intermediate for further synthetic transformations. The ozonolysis of this group was investigated, producing derivatives of beta-keto-delta-methylamino esters and beta-keto aldehydes which could be subsequently converted to heterocycles. The restriction to rotation of the C-N bond in N-benzoyl-1-(1,4-cyclohexadien-1-yl)-N-methyl-2-propanamine is described.     

A potent, versatile disulfide-reducing agent from aspartic acid

Dithiothreitol (DTT) is the standard reagent for reducing disulfide bonds between and within biological molecules. At neutral pH, however, >99% of DTT thiol groups are protonated and thus unreactive. Herein, we report on (2S)-2-amino-1,4-dimercaptobutane (dithiobutylamine or DTBA), a dithiol that can be synthesized from l-aspartic acid in a few high-yielding steps that are amenable to a large-scale process. DTBA has thiol pK(a) values that are ~1 unit lower than those of DTT and forms a disulfide with a similar E°' value. DTBA reduces disulfide bonds in both small molecules and proteins faster than does DTT. The amino group of DTBA enables its isolation by cation-exchange and facilitates its conjugation. These attributes indicate that DTBA is a superior reagent for reducing disulfide bonds in aqueous solution.