Synthesis and metal complexation of chiral 3-mono-or 3, 3-bis-allyl-2-hydroxypyrrolopyrazine-1, 4-diones

A novel synthesis of chiral cyclic hydroxamic acids (4, 6, 8 and 10) related to cyclodipeptides is described. The crucial reduction of the nitro group of the N-nitroacetyl derivatives of (S)-α-amino acid esters is brought about by zinc-aq. ammonium chloride. The FeIII and CuII complexes of one such cyclic hydroxamic acid 10a have been prepared and their DNAse activity investigated

Chemical cleavage of plasmid DNA by Cu(II), Ni(II) and Co(III) desferal complexes

It is demonstrated that the Cu(II), Co(III) and Ni(II) complexes of a siderophore chelating drug desferal cleave DNA, in contrast to the corresponding Fe(II) complex which does not bring about DNA scission. Hydroxy radical scavengers inhibit the cleavage reaction

Regioselective allylations of pyrimidine ribonucleosides using Pd(0) catalyst

A novel procedure for regiospecific O-allylation of pyrimidine ribonucleosides is reported by using Pd(PPh<SUB>3</SUB>)<SUB>4</SUB>-allyl ethyl carbonate reagent to synthesize 2'-O-allyluridine and 2'-O-allylcytidine. 3-N-allylation of the pyrimidine ring is prevented by protection of uridine imide function by 4-O-(2,5-dimethylphenyl) group which can be transformed to 4-oxo function of uridine or exocyclic amino function of cytidine

Quinone-capped porphyrins: n.m.r studies of static and dynamic stereochemistry and co-ordination properties

<SUP>1</SUP>H N.m.r, spectroscopy has been used to investigate the shape, motion, and flexibility of two of the title compounds, and their magnesium derivatives, and to probe the co-ordinative properties of the latter. Coupling constant and n.O.e. results for the porphyrin moiety are analysed in terms of two possible conformations. The cap moiety for simple alkyl-capped porphyries appears to have a well defined shape. In the title compounds, however, the quinone ring is flipping rapidly and a temperature dependent 'breathing' is observed; the quinone is closer on average to the porphyrin in the compound with additional methylene groups in the cap. At ambient temperature molecular tumbling is severely hindered in these propellor-shaped molecules leading to rapid relaxation and broad lines, but resolution improves substantially on warming. Pyridine titration data for the magnesium derivatives indicate that the metal ion is out-of-plane 5-co-ordinate, bound intramolecularly to a quinone carbonyl, and that it can accept a 6th ligand from the unhindered side of the porphyrin, moving into the plane and pulling the quinone towards the porphyrin. The average orientation of the quinone ring appears to be perpendicular to the porphyrin

Effect of fluidics on corneal endothelial cell density, central corneal thickness, and central macular thickness after phacoemulsification with torsional ultrasound

Aim: To study the relative effects of high and low fluidic parameters on endothelial cell density (ECD), central corneal thickness (CCT), and central macular thickness (CMT) after phacoemulsification with torsional ultrasound. Settings and Design: Prospective, randomized clinical trial based on a tertiary eye hospital. Subjects and Methods: The study included 65 patients in each group. Patients were randomized to either the high or the low flow group using a computerized random number table. The study was patient and examiner masked. All patients underwent phacoemulsification with torsional ultrasound. Visual acuity, ECD, CCT, and CMT were measured for all patients preoperatively at 2 weeks and 6 weeks postoperatively. Statistical Analysis Used: The Shapiro–Wilks test was used to assess the normality of the data. Mann–Whitney U-test with the P value set at 0.05 was used to compare the two groups. Results: Cumulative dissipated energy was significantly higher in the low flow group (16.44 ± 9.07 vs. 11.74 ± 6.68; P = 0.002). No statistically significant difference was noted between the two groups in the ECD, CCT, CMT, or corrected distance visual acuity at the end of 6 weeks. Conclusions: No significant difference was noted in the postoperative outcome between high and low flow groups. Parameters can be modified to suit the surgeon's preference, as both high and low flow parameters were found to have comparable postoperative outcomes

Structural investigation of lac resin. Part 12. 10-epi- and 2-epi, 10-epi-Shellolic acids and some allylic rearrangements

The nature, reactivity, and acid-catalysed isomerisations of the allyl system in shellolic acid and its 2-epimer are discussed. The configurations of substituents at C-10 in these cedrene derivatives are correlated with their spectral characteristics. The relevance of the results to the complexity of shellac is indicated