			Home About us Contact

Oxo Group (oxo + group)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Synthesis and Enzymic Hydrolysis of Oligoribonucleotides Incorporating 3-Deazaguanosine: The Importance of the Nitrogen-3 Atom of Single Conserved Guanosine Residues on the Catalytic Activity of the Hammerhead Ribozyme

HELVETICA CHIMICA ACTA, Issue 8 2003
Frank Seela
Four base-modified hammerhead ribozyme/substrate complexes were constructed in which single guanosine (1) residues were replaced by 3-deazaguanosine (2) in the positions G5, G8, GL2.1, and G12. The base-modified ribozyme complexes were prepared by solid-phase synthesis of oligoribonucleotides employing the novel phosphoramidite 3 derived from 2. Phosphoramidite 3 carried a phenoxyacetyl group at the amino function and a diphenylcarbamoyl residue at the oxo group of the nucleobase. The 2,-hydroxy group was blocked with a triisopropylsilyl residue. Kinetic analysis of the phosphodiester hydrolysis showed a moderate decrease of the ribozyme catalytic activity when the residues G5 or G8 were replaced by 3-deazaguanosine and a 200-fold decrease when G12 was substituted. A 6-fold catalytic increase occurred when 3-deazaguanosine was replacing GL2.1 in the loop region. The data indicate that the N(3) atom of compound 2, in particular at position G12 is critical for the ribozyme activity. [source]

Aromatization and ring cyclization: A better understanding on the ring cyclization mechanism of 3-amino-6-hydrazino-1,2,4-triazin-5(2H)-one reacted with acetic acid in N,N -dimethylformamide

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2005
Long-Chih Hwang
In this paper we report that the title compound (3) reacts with excess N,N -dimethylformamide (DMF) containing two equivalents of acetic acid to afford 6-amino-1,2,4-triazolo[3,4- f][1,2,4]triazin-8(7H)-one (1). When 3-amino-2-benzyl-6-hydrazino-1,2,4-triazin-5(2H)-one (6), the N-2 benzylated derivative of 3, is treated under the same conditions, ring cyclization does not occur; instead, 3-amino-2-benzyl-6-(2-formyl-hydrazino)-1,2,4-triazin-5(2H)-one (7) is formed. Single-crystal X-ray analysis of a 3-ethyl derivative of compound 1 reveals the predominant tautomeric structure to be the 7H -tautomer (7H - 1). From these results, we propose a reasonable cyclization mechanism that incorporates two important points: (1) the tautomerism of the N-2 hydrogen with the C-5 oxo group aromatizes the 1,2,4-triazine ring, and (2) the DMF is proto-nated by acetic acid on the nitrogen atom, then deamination occurs where DMF is attacked by the 6-hydrazino group of 3 or 6. [source]

Identification and fragmentation of hydrolyzed aluminum species by electrospray ionization tandem mass spectrometry

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2004
Arja Sarpola
Abstract Earlier characterization of some hydrolysis products of AlCl3·6H2O was confirmed by electrospray ionization tandem mass spectrometry with increasing collision energy of projectile ions. At lower collision energies, the aqua ligands were stripped off. At higher energies, two hydroxo groups formed a bridging oxo group with loss of one water molecule. Aluminum complexes could also capture aqua ligands in the collision chamber so long as the parent ion did not fragment, and the fragment ion spectra broadened toward higher m/z values. The chloro ligands were eliminated as hydrochloric acid. The aluminum cores remained highly intact. Copyright © 2004 John Wiley & Sons, Ltd. [source]

5-Hydroxyalkyl derivatives of tert -butyl 2-oxo-2,5-dihydro-1H -pyrrole-1-carboxylate: diastereoselectivity of the Mukaiyama crossed-aldol-type reaction

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2009
Olivier Vallat
The title compounds, rac -(1,R,2R)- tert -butyl 2-(1,-hydroxyethyl)-3-(2-nitrophenyl)-5-oxo-2,5-dihydro-1H -pyrrole-1-carboxylate, C17H20N2O6, (I), rac -(1,S,2R)- tert -butyl 2-[1,-hydroxy-3,-(methoxycarbonyl)propyl]-3-(2-nitrophenyl)-5-oxo-2,5-dihydro-1H -pyrrole-1-carboxylate, C20H24N2O8, (II), and rac -(1,S,2R)- tert -butyl 2-(4,-bromo-1,-hydroxybutyl)-5-oxo-2,5-dihydro-1H -pyrrole-1-carboxylate, C13H20BrNO4, (III), are 5-hydroxyalkyl derivatives of tert -butyl 2-oxo-2,5-dihydropyrrole-1-carboxylate. In all three compounds, the tert -butoxycarbonyl (Boc) unit is orientated in the same manner with respect to the mean plane through the 2-oxo-2,5-dihydro-1H -pyrrole ring. The hydroxyl substituent at one of the newly created chiral centres, which have relative R,R stereochemistry, is trans with respect to the oxo group of the pyrrole ring in (I), synthesized using acetaldehyde. When a larger aldehyde was used, as in compounds (II) and (III), the hydroxyl substituent was found to be cis with respect to the oxo group of the pyrrole ring. Here, the relative stereochemistry of the newly created chiral centres is R,S. In compound (I), O,H...O hydrogen bonding leads to an interesting hexagonal arrangement of symmetry-related molecules. In (II) and (III), the hydroxyl groups are involved in bifurcated O,H...O hydrogen bonds, and centrosymmetric hydrogen-bonded dimers are formed. The Mukaiyama crossed-aldol-type reaction was successful when using the 2-nitrophenyl-substituted hydroxypyrrole, or the unsubstituted hydroxypyrrole, and boron trifluoride diethyl ether as catalyst. The synthetic procedure leads to a syn configuration of the two newly created chiral centres in all three compounds. [source]

(18-Crown-6)-,-oxo-hexakis(tetrahydroborato)diuranium(IV): an unprecedented asymmetric dinuclear complex

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2006
Claude Villiers
In the title compound, (1,4,7,10,13,16-hexaoxacyclooctadecane-1,6O)-,-oxo-1:2,2O:O -hexakis(tetrahydroborato)-1,3H;2,2H;2,2H;2,3H;2,3H;2,3H -diuranium(IV), [U2(BH4)6O(C12H24O6)], one of the U atoms (U1), located at the centre of the crown ether moiety, is bound to the six ether O atoms, and also to a tridentate tetrahydroborate group and a ,-oxo atom in axial positions. The other U atom (U2) is bound to the same oxo group and to five tetrahydroborate moieties, three of them tridentate and the other two bidentate. The two metal centres are bridged by the ,-oxo atom in an asymmetric fashion, thus giving the species (18-crown-6)(,3 -BH4)U=(,-O),U(,3 -BH4)3(,2 -BH4)2, in which the U1=O and U2,O bond lengths to the ,-O atom [1.979,(5) and 2.187,(5),Å, respectively] are indicative of the presence of positive and negative partial charges on U1 and U2, respectively. [source]