NMR investigation into the dynamic behaviour of a novel C2-symmetric macrocyclic ligand

The variable-temperature (1)H NMR spectra of a tosylated triazacyclononane are reported. The spectra show a dynamic process which is assigned to hindered rotation about the amide-like N--S bonds, and a value for the free energy of activation for the rotations is derived, DeltaG* = 50.2 kJ mol(-1) at 273 K. Steric and electronic factors which influence the barrier are discussed.

Isolated mild fetal ventriculomegaly

Ventriculomegaly is an excess of fluid in the lateral ventricles within the developing cerebrum. It is usually diagnosed at a routine fetal anomaly scan at 18-22 weeks gestation. Management of the condition and counselling of parents are difficult, as the cause, absolute risk, and degree of resulting handicap cannot be determined with confidence.

The synthesis of unsymmetrically N-substituted chiral 1,4,7-triazacyclononanes

A number of chiral unsymmetrically N-substituted 1,4,7-triazacyclononane ligands have been prepared by modular methods. The key step in the synthesis centres on the macrocyclisation of three tertiary amide precursors under standard Richman-Atkins conditions which allows for subsequent N-functionalisation.

Rare and unexpected coordination to copper(ii) by a tertiary amide in a macrocyclic ligand

Incorporation of a tertiary amide donor within the framework of a C(2)-symmetric analogue of 1,4,7-triazacyclononane derived from L-valine results in the isolation of a very rare example of a classical Werner copper(II) complex in which tertiary amide coordination occurs; despite the monomeric nature of the complex in the solid state, frozen solution EPR studies reveal the presence of a triplet ground state consistent with a dimeric species.

Structure, modelling and dynamic behaviour of aza- and azaoxamacrocyclic ligands derived from (R,R)-1,2-diaminocyclohexane

Investigations into the conformational behaviour of macrocyclic ligands 5 and 6 derived from (R,R)-1,2-diaminocyclohexane have been undertaken using molecular modelling, single crystal X-ray diffraction and variable temperature 1H NMR spectroscopy. These have revealed that the lowest energy conformers in both cases do not possess the expected C2-element of symmetry, which can only be accessed at higher temperatures. Instead both molecules exist as C1-conformers at room temperature and in the solid state. In solution a range of dynamic exchange processes is observed which result, in part from the inherent strain in these fused bicyclic systems. An unexpected but characteristic feature of the C1-symmetric conformers is highlighted by the presence of a signal at unexpectedly low field in their 1H NMR spectra due to the interaction of two of the sulfonyl oxygen atoms with one of the bridgehead hydrogen atoms.

Gene-specific chromatin damage in human spermatozoa can be blocked by antioxidants that target mitochondria

Incubation of gradient purified human spermatozoa, which are routinely maintained in media prior to IVF and intracytoplasmic sperm injection (ICSI), induced DNA strand breaks (up to 89 nicks x 10(-3) bp) and chromatin release. Unlike highly dispersed Alu repeat sequences, the centromeric heterochromatin was much less susceptible to endonuclease attack. In addition to chromatin release, the permeability of the sperm membrane was altered as evidenced by reduced accessibility of sperm nuclei to decondensation factors in mouse embryo extracts. Hybridization of cDNA microarrays with DNA released from spermatozoa revealed a consistent hypersensitivity of certain genes to endogenous cleavage including TP53, VHL (tumour suppressors), BRCA1 (breast cancer), NOS1 (neurotransmitter), PECAM1, FLT1 (angiogenesis) and CDKN1C (cell cycle/imprinted). N-tert-butyl hydroxylamine (NTBH), a derivative of the anti-teratogenic alpha-phenyl-N-t-butyl nitrone (PBN) and synthetic superoxide dismutase (SOD)/catalase mimetics inhibited chromatin release and sustained or dissipated relative mitochondrial membrane potential. Together, these results show a link between the hyperactivation of sperm mitochondria and chromosomal damage of specific genes in vitro, and that the potential risk of disruption of paternally contributed genes can be circumvented by antioxidants which are known to target mitochondria.

Aquachloro[N,N'-ethylenebis(salicylideneiminato)]manganese(III)

The title compound, aquachloro(2,2'-[1,2-ethanediylbis(nitrilomethylidyne)]diphenolato-kappa4O,N,N',O')manganese(III),[MnCl(C(16)H(14)N(2)O(2))(H(2)O)], is a neutral manganese(III) complex with a pseudo-octahedral metal centre. The equatorial plane comprises the four donor atoms of the tetradentate Schiff base ligand [Mn-O 1.886 (4) and 1.893 (4) A, and Mn-N 1.978 (5) and 1.982 (5) A], with a water molecule [Mn-O 2.383 (4) A] and a Cl- ligand [Mn-Cl 2.4680 (16) A] completing the coordination sphere. The distorted geometry is highlighted by the marked displacement of the Mn(III) ion out of the least-squares plane of the four Schiff base donor atoms by 0.165 (2) A. These monomeric Mn(III) centres are then linked into a polymeric array via hydrogen bonds between the coordinated water molecule and the phenolic O-atom donors of an adjacent Mn(III) centre [O-H.O 2.789 (5) and 2.881 (5) A].

Hypertension in the newborn baby

Hypertension is rare in the newborn infant. It has a cumbersome definition and diagnosis, and screening is not justified using present definitions and technology. Thresholds for starting antihypertensive treatment in the first month of life are not clear, and the treatment is difficult, with idiosyncratic responses to drugs in neonates with varying renal and hepatic function.

Events before the diagnosis of a pneumothorax in ventilated neonates

AIM

To examine the relation of overventilation and other clinical events to the development of pneumothoraces in ventilated neonates.

METHODS

A case-control study.

RESULTS

Fifty three (8.7%) of 606 ventilated neonates developed a pneumothorax. Eighteen (34%) cases and 23 (43%) controls were unintentionally overventilated (PaCO(2) < 4 kPa) at some time before the pneumothorax developed in the cases (odds ratio (OR) = 0.78, 95% confidence interval (CI) 0.48 to 1.27). In the three hours before the diagnosis of pneumothorax, more cases than controls were reintubated (21/53 v 4/53; OR = 5.25, 95% CI 1.9 to 14.3), and also in seven cases (one control) the mean airway pressure was increased, whereas in nine controls (no cases) it was reduced (chi(2) = 12.0, df = 2, p = 0.001). Seven of 18 neonates diagnosed by transillumination had undergone no clinical procedures before diagnosis compared with five of 35 diagnosed radiologically (OR = 2.7, 95% CI 1.0 to 7.4).

CONCLUSIONS

Unintentional overventilation was not associated with pneumothoraces. In the hours before diagnosis, there was increased clinical intervention, including reintubation; this was less so in those diagnosed by transillumination. The study did not elucidate whether such interventions caused the pneumothorax or were secondary to a failure to diagnose it.

Catalytic Allylic Oxidation of Alkenes Using an Asymmetric Kharasch-Sosnovsky Reaction

Kharasch and Sosnovsky reported the allylic oxidation of alkenes to give racemic allylic benzoates. This could be achieved efficiently using a tert-butyl perester as the oxidant, in the presence of a copper or cobalt salt. The use of C(2)-symmetric bis(oxazoline) ligands in the presence of copper(I) triflate with cyclic olefinic substrates gave the first synthetically useful asymmetric variant. The enantioselective control was good (up to 84 % ee) although yields were variable. In all cases the facial preference of the newly formed C-O bond was the same giving an S configuration at the allylic stereocenter. Lower stereocontrol was observed for large-ring alkenes and substantially reduced enantioselectivities were found with open-chain alkenes. This reaction has been further screened using a variety bis(oxazoline) and proline-derived ligands, which give a direct correlation between the chirality of the ligand and the enantioselectivity obtained. Individual substrates were found to be extremely sensitive to both the ligand structure and copper salt used as well as the presence of additives such as zinc, hydrazine, and molecular sieves.

Ophthalmic Pseudomonas infection in infancy

Four infants developed invasive Pseudomonas aeruginosa ophthalmic infections between 5 and 90 days of age. Three died from septicaemia, and the fourth required enucleation of one eye. Absent red reflexes or other eye signs in a septicaemic infant merit urgent ophthalmological assessment for endophthalmitis, in particular, Pseudomonas.