Synthesis of (+)-Cortistatin A

Steroids have historically elicited attention from the chemical sciences owing to their utility in living systems, as well as their intrinsic and diverse beauty.1 The cortistatin family (Figure 1, 1-7 and others),2 a collection of unusual, marine 9-(10,19)-abeo-androstane steroids, is certainly no exception; aside from challenging stereochemistry and an odd bricolage of functional groups, the salient feature of these sponge metabolites is, inescapably, their biological activity. Cortistatin A, the most potent member of the small family, inhibits the proliferation of human umbilical vein endothelial cells (HUVECs, IC50) 1.8 nM), evidently with no general toxicity toward either healthy or cancerous cell lines (IC50(testing cells)/IC50(HUVECs) g 3300).2a From initial pharmacological studies, binding appears to occur reversibly, but to an unknown target, inhibiting the phosphorylation of an unidentified 110 kDa protein, and implying a pathway that may be unique to know

Enantiodivergent Formation of C−P Bonds: Synthesis of P‑Chiral Phosphines and Methylphosphonate Oligonucleotides

Phosphorus Incorporation (PI, abbreviated Π) reagents for the modular, scalable, and stereospecific synthesis of chiral phosphines and methylphosphonate nucleotides are reported. Synthesized from translimonene oxide, this reagent class displays an unexpected reactivity profile and enables access to chemical space distinct from that of the Phosphorus−Sulfur Incorporation reagents previously disclosed. Here, the adaptable phosphorus(V) scaffold enables sequential addition of carbon nucleophiles to produce a variety of enantiopure C−P building blocks. Addition of three carbon nucleophiles to Π, followed by stereospecific reduction, affords useful P-chiral phosphines; introduction instead of a single methyl group reveals the first stereospecific synthesis of methylphosphonate oligonucleotide precursors. While both Π enantiomers are available, only one isomer is requiredthe order of nucleophile addition controls the absolute stereochemistry of the final product through a unique enantiodivergent design

Wild turkey biology and habitat management in Missouri (2017)

Not much more than a half century ago, Missouri's wild turkey population was in danger of disappearing from the landscape. By the early 1950s, it was estimated that fewer than 2,500 turkeys were left in only 14 Missouri counties. Their restoration is one of the state's great conservation success stories. Many private landowners in Missouri are interested in creating and maintaining habitat for wild turkeys. This guide provides recommendations for doing just that. Before learning about specific habitat management practices, it is important to build basic knowledge about turkey biology, population dynamics and habitat needs. This broader information will help landowners and managers better understand the value of implementing specific habitat management practices

Serine-Selective Bioconjugation.

This Communication reports the first general method for rapid, chemoselective, and modular functionalization of serine residues in native polypeptides, which uses a reagent platform based on the P(V) oxidation state. This redox-economical approach can be used to append nearly any kind of cargo onto serine, generating a stable, benign, and hydrophilic phosphorothioate linkage. The method tolerates all other known nucleophilic functional groups of naturally occurring proteinogenic amino acids. A variety of applications can be envisaged by this expansion of the toolbox of site-selective bioconjugation methods

Cirrus clouds

Andrew J. Heymsfield, Martina Kramer, Anna Luebke, Phil Brown, Daniel J. Cziczo, Charmaine Franklin, Ulrike Lohmann, Greg McFarquhar, Zbigniew Ulanowski and Kristof Van Trich, American Meteorological Society , January 2017, this article has been published in final form at DOI: http://dx.doi.org/10.1175/AMSMONOGRAPHS-D-16-0010.1 Published by AMS Publications © 2017 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (http://www.ametsoc.org/PUBSCopyrightPolicy).The goal of this article is to synthesize information about what is now known about one of the three main types of clouds, cirrus, and to identify areas where more knowledge is needed. Cirrus clouds, composed of ice particles, form primarily in the upper troposphere, where temperatures are generally below -30°C. Satellite observations show that the maximum-occurrence frequency of cirrus is near the tropics, with a large latitudinal movement seasonally. In-situ measurements obtained over a wide range of cloud types, formation mechanisms, temperatures, and geographical locations indicate that the ice water content and particle size generally decrease with decreasing temperature, whereas the ice particle concentration is nearly constant or increase slightly with decreasing temperature. High ice concentrations, sometimes observed in strong updrafts , results from homogeneous nucleation. The satellite-based and in-situ measurements indicate that cirrus ice crystals typically depart from the simple, idealized geometry for smooth hexagonal shapes, indicating complexity and/or surface roughness. Their shapes significantly impact cirrus radiative properties and feedbacks to climate. Cirrus clouds, one of the most uncertain components of general circulation models (GCM), pose one of the greatest challenges in predicting the rate and geographical pattern of climate change. Improved measurements of the properties and size distributions and surface structure of small ice crystals — about 20 μm, and identifying the dominant ice nucleation process — heterogeneous versus homogeneous ice nucleation, under different cloud dynamical forcings, will lead to a better representation of their properties in GCM and in modeling their current and future effects on climate.Peer reviewe

Rapid Alternating Polarity as a Unique Tool for Synthetic Electrochemistry

Electrosynthesis, driven by renewable energy, is a powerful method for accessing useful chemical reactivity in a sustainable fashion. Typically, electrochemical reactions have been carried out using direct current (DC), where electrons flow in a single direction. In contrast, utilization of alternating current (AC) has been largely unexplored in synthetic electrochemistry despite its wide applications in our daily life. This could stem from a historical perception regarding the lack of unique reactivity/selectivity that would result from using such a waveform, as well as the absence of readily available instrumentation to remove the engineering barrier for mass adoption. A breakthrough in this area is the introduction of rapid alternating polarity (rAP), which alternates the polarity of an electrode in the millisecond timescale. This mode of current delivery, now implemented in the widely employed potentiostat, ElectraSyn2.0, enables access to unique reactivity and selectivity in organic synthesis that are challenging or currently impossible to achieve by any known method (chemical or electrochemical). The remarkable chemoselectivity and simplicity of rAP open new vistas in modern synthetic electrochemistry

Ni-Catalyzed Enantioselective Decarboxylative Acylation: Rapid, Modular Access to a-Amino Ketones

A new approach to the enantiocontrolled synthesis of alpha-amino ketone derivatives is disclosed by employing a decarboxylative acylation strategy. Thus, when an acyl chloride and an alpha-amido-containing redox-active ester are exposed to Ni-catalysis, a chiral ligand, and metal reductant, alpha-amido ketones are produced in good yield and high ee. The reaction exhibits broad substrate scope, can be easily scaled up, and is applied to dramatically simplify the synthesis of several known structures