RHODIUM(I)-CATALYZED CYCLOISOMERIZATION OF NITROGEN TETHERED ENE-ALLENES: FORMATION OF TETRAHYDROAZEPINES

Abstract: A novel cycloisomerization process involving nitrogen-tethered 1,6-ene-allenes has been realized. Subjecting ene-allene 9 to rhodium biscarbonyl chloride dimer produces tetrahydroazepine 10 in moderate to high yields. Substituting the allene moiety with the bulky tert-butyl-group (R4 = t-Bu), while employing a trans-alkene tether, afforded the corresponding azepines in the highest yields. This formal Alder-ene transformation tolerated not only a variety of alkyl-substituents on both the alkene and allene portions but also silyl-[R2 = SiMe3, SiMe2Bn; R4 = Si(i-Pr)3] and phenyl-(R2 = Ph, R4 = Ph) substituents. A deuterium labeling study aided in the postulation of two possible mechanisms for this cycloisomerization. During the course of this investigation, a novel carbon monoxide insertion reaction was observed. Our findings to date are reported and discussed herein

Biophysical regulation of stem cell behavior within the niche.

Stem cells reside within most tissues throughout the lifetimes of mammalian organisms. To maintain their capacities for division and differentiation and thereby build, maintain, and regenerate organ structure and function, these cells require extensive and precise regulation, and a critical facet of this control is the local environment or niche surrounding the cell. It is well known that soluble biochemical signals play important roles within such niches, and a number of biophysical aspects of the microenvironment, including mechanical cues and spatiotemporally varying biochemical signals, have also been increasingly recognized to contribute to the repertoire of stimuli that regulate various stem cells in various tissues of both vertebrates and invertebrates. For example, biochemical factors immobilized to the extracellular matrix or the surface of neighboring cells can be spatially organized in their placement. Furthermore, the extracellular matrix provides mechanical support and regulatory information, such as its elastic modulus and interfacial topography, which modulate key aspects of stem cell behavior. Numerous examples of each of these modes of regulation indicate that biophysical aspects of the niche must be appreciated and studied in conjunction with its biochemical properties

Modelling Inflation in Australia

This paper estimates a range of single-equation models of inflation for Australia. We find that traditional models, such as the expectations-augmented standard Phillips curve or mark-up models, outperform the more micro-founded New-Keynesian Phillips curve (NKPC) in explaining trimmed mean inflation, both in terms of in-sample fit and significance of coefficients. This in large part reflects the weak instruments problem in the estimation of the NKPC, and is partly corrected by including a direct measure of inflation expectations, but we still find that the unemployment rate or growth in marginal costs (unit labour cost and import prices) provides a better fit than either the output gap or level of real marginal costs. These traditional models also perform well in out-of-sample tests, relative to alternative models and some common benchmarks, with the standard Phillips curve clearly superior to these benchmarks on this test. As inflation has become better anchored and hence less variable, the magnitude of the errors of the single-equation models has declined, although the explanatory power (in terms of R-squared) has fallen together with this greater stability. We also investigate the empirical importance of some other variables that are commonly cited as determinants of inflation, and find little evidence that either commodity prices or the growth rate of money directly influence Australian underlying inflation.inflation; modelling