A series of quinoxaline 1,4-di-N-oxide analogues were prepared from benzofurazan N-oxide derivatives and β-diketone ester compounds by the improved Beirut reaction. The structures of the target products were characterized by NMR, MS, IR and elemental analysis measurements, and that of 2-carbomethoxy-3-hydroxyquinoxaline- di-N-oxide was further confirmed by single-crystal X-ray diffraction. Its ...

Tetrazoles remain a challenge to photochemists. Photolysis leads to cleavage of the tetrazolyl ring, may involve various photodegradation pathways and may produce a diversity of photoproducts, depending on the structure and conformational flexibility of the substituents and the possibility of tautomerism. If the photochemistry of tetrazoles is considered within the frame of synthetic applicatio...

The structures of new protein farnesyltransferase inhibitors, andrastins A-C, were elucidated. The cyclopentane ring of andrastins exhibited keto-enol tautomerism, which made the structure hard to elucidate. Therefore, the structure of andrastin A was elucidated by INADEQUATE and 13C-13C couplings using 13C-labeled andrastin A. The absolute configuration of the p-bromobenzoyl derivative of andr...

In the title compound, C(14)H(9)NO(2), a static disorder exists between the keto-oxime and hy-droxy-nitroso tautomers, in an approximate ratio of 4.6:1, based on refined occupancies for disordered parts. No inter-molecular hydrogen bonding is present in the crystal structure. Instead, both tautomers exhibit similar intra-molecular O-H⋯O hydrogen bonds.

The single crystal X-ray structure of the DMSO solvate of cyameluric acid C6N7O3H3 · 3DMSO, 2b’ has been determined. The results show that the most stable tautomer of solid cyameluric acid is the tri-keto form 2b with C3h symmetry. 1H and 13C NMR data indicate that this isomer is also present in solution, with slow interchange of the N-H protons. This confirms previous theoretical results altho...

Proton migration in protonated glycylglycylglycine (GGG) has been investigated by using density functional theory at the B3LYP/6-31++G(d,p) level of theory. On the protonated GGG energy hypersurface 19 critical points have been characterized, 11 as minima and 8 as first-order saddle points. Transition state structures for interconversion between eight of these minima are reported, starting from...

A new cobalt bis(semiquinone) valence tautomer is reported featuring a terthienyl substituent, which undergoes electropolymerization to produce a valence tautomeric conducting metallopolymer.

Redox regulation of protein tyrosine phosphatase 1B (PTP1B) involves oxidative conversion of the active site cysteine thiolate into an electrophilic sulfenyl amide residue. Reduction of the sulfenyl amide by biological thiols regenerates the native cysteine residue. Here we explored fundamental chemical reactions that may enable covalent capture of the sulfenyl amide residue in oxidized PTP1B. ...