No abstract

A new intermolecular, stereo- and regioselective iron-catalyzed 1,4-addition of alpha-olefins to 1,3-dienes using as low as 1 mol % of an iminopyridine-ferrous chloride complex was developed. Importantly, both double bonds of the linear 1,4-diene addition products are obtained with absolute stereocontrol.

A highly enantioselective (up to 97.5% ee) and diastereoselective (95:5 dr trans/cis) Cu(I)-catalyzed cyclopropanation of alkenes using phenyliodonium ylide generated in situ from iodosobenzene and methyl nitroacetate is reported. The cyclopropanation took place with high enantioselectivity for a wide range of alkenes, and the reaction was performed at room temperature. 1-Nitrocyclopropyl esters are versatile building blocks to access the corresponding cyclopropane amino esters and aminocyclopropanes in two and three steps, respectively, from commercially available products.

Early embryonic cleavages are mostly regulated by maternal components then control of development progressively depends on newly synthesized zygotic products. The timing of the first cleavages is a way to assess embryo quality. The goal of this study was to evaluate the duration of the fourth cell cycle, at the time of maternal-to-zygotic transition (MZT) in in vitro-produced bovine embryos by means of cinematographic analysis. We found that 75% of the embryos displayed a long fourth cycle (43.5 +/- 5.4 h) whereas the remaining embryos had a very short fourth cell cycle (8.9 +/- 2.9 h). Both groups did not differ in cleavage rhythm up to the eight-cell stage and timing of cavitation and blastocyst expansion was identical. However, embryos with a short fourth cell cycle had a better blastocyst rate than embryos with a long cycle (59% versus 38%, P < 0.01). Total cell number, inner cell mass (ICM):total cell ratio, and hatching rate were identical for blastocysts produced from embryos with either a long or a short fourth cell cycle. In a second experiment, we showed that increasing the oxygen tension, from 5% to 20%, decreased the percentage of embryos with a short fourth cell cycle, from 25% to 11% (P < 0.01), indicating that suboptimal culture conditions can influence the length of this cycle. Finally, we investigated whether fourth cell cycle duration could be influenced by transcription inhibition. With alpha-amanitin added at 18 h postinsemination (HPI), cleavage was reduced (66% versus 79%) and, at 70 HPI, the 9- to 16-cell rate increased (50% versus 25%) concomitantly with a 5- to 8-cell rate decrease (16% versus 47%). A similar pattern was observed when the drug was added at 6 HPI or 42 HPI but not at 0 HPI. Cinematographic analysis revealed that alpha-amanitin increased the first cell cycle duration whereas the second and third cell cycles were not affected. With the drug, one third of the embryos could develop up to the 9- to 16-cell stage and they all had a short fourth cell cycle (11.2 +/- 3.7 h) with a good synchrony of cleavage between blastomeres. These results suggest that duration of the fourth cell cycle of bovine embryo, during the MZT, is under a zygotic transcriptional control that can be affected by oxidative conditions.

The sequence of octarellin I, the first de novo (beta/alpha)8 polypeptide, was revised according to several criteria, among others the symmetry of the sequence, beta-residue volume and hydrophobicity, and charge distribution. These considerations and the overall conclusions drawn from the first design led to two new sequences, corresponding to octarellins II and III. Octarellin II retains perfect 8-fold symmetry. Octarellin III has the same sequence as octarellin II, except for the beta-strands which exhibit a 4-fold symmetry. The two proteins were produced in Escherichia coli. Infrared and CD spectral analyses of octarellins II and III reveal a high secondary structure content. Non-denaturing gel electrophoresis, molecular sieve chromatography and analytical ultracentrifugation suggest that both of these second-generation artificial polypeptides exist as a mixture of a monomer and a dimer form. Octarellins II and III are at least 10 times more soluble than octarellin I. Urea-induced unfolding followed by fluorescence emission suggests that the tryptophan residues, designed to be buried in the (beta/alpha)8, are indeed packed in the hydrophobic core of both proteins. However, octarellin III displays a higher stability towards urea denaturation, indicating that introducing 4-fold symmetry into the beta-barrel might be important for stability of the overall folding.

Somatostatin receptor 2 (SSTR2) is frequently overexpressed on several types of solid tumors, including neuroendocrine tumors and small-cell lung cancer. Peptide agonists of SSTR2 are rapidly internalized upon binding to the receptor and linking a toxic payload to an SSTR2 agonist is a potential method to kill SSTR2-expressing tumor cells. Herein, we describe our efforts towards an efficacious SSTR2-targeting cytotoxic conjugate; examination of different SSTR2-targeting ligands, conjugation sites, and payloads led to the discovery of 22 (PEN-221), a conjugate consisting of microtubule-targeting agent DM1 linked to the C-terminal side chain of Tyr3–octreotate. PEN-221 demonstrates in vitro activity which is both potent (IC50 = 10 nM) and receptor-dependent (IC50 shifts 90-fold upon receptor blockade). PEN-221 targets high levels of DM1 to SSTR2-expressing xenograft tumors, which has led to tumor regressions in several SSTR2-expressing xenograft mouse models. The safety and efficacy of PEN-221 is currently under evaluation in human clinical trials.

Background: Antivirals must often be given in combinations to avoid rapid emergence of resistance. Results: We identified and structurally characterized protease inhibitors that maintain potency against genotype and resistant variants. Conclusion: Pan-variant potency was achieved by targeting invariant regions and incorporating flexibility where pocket variability occurs. Significance: Such inhibitors may yield simplified and/or more successful treatments for hepatitis C infections.

No abstract