Use of Calculated Physicochemical Properties to Enhance Quantitative Response When Using Charged Aerosol Detection.

Universal quantitative detection without the need for analyte reference standards would offer substantial benefits in many areas of analytical science. The quantitative capability of high-performance liquid chromatography (HPLC) with charged aerosol detection (CAD) was investigated for 50 compounds with a wide range of physical and chemical properties. It is widely believed that CAD is a mass detector. Quantification of the 50 compounds using a generic calibrant and mass calibration achieved an average error of 11.4% relative to 1H NMR. Correction factors are proposed that estimate the relative surface area of particles in the detector, taking into account the effects of the density and charge of analytes. Performing these corrections and quantifying with surface area calibration, rather than mass, shows considerably improved linearity and uniformity of detection, reducing the average error relative to 1H NMR to 7.1%. The accuracy of CAD quantification was most significantly improved for highly dense compounds, with traditional mass calibration showing an average error of 34.7% and the newly proposed surface area calibration showing an average error of 5.8%.

Improving the passive permeability of macrocyclic peptides: Balancing permeability with other physicochemical properties.

A number of methods to improve the passive permeability of a set of cyclic peptides have been investigated using 6- and 7-mer macrocyclic templates. In many cases the peptides were designed by molecular dynamics calculations to evaluate the methods. The aim of this study was not only to improve passive permeability, but also to balance permeability with other physicochemical properties with the goal of understanding and applying the knowledge to develop active cyclic peptides into drug candidates. Evaluation of the methods herein suggest that increasing passive permeability often occurs at the expense of solubility and lipophilicity. Computational methods can be useful when attempting to predict and design features to balance these properties, though limitations were observed.

NMR quantification using an artificial signal.

We have developed QUANTAS (QUANTification by Artificial Signal), which is a software-based protocol for concentration measurement by NMR. QUANTAS is an absolute intensity external standard method for quantification by NMR that compensates for various experimental parameters. It is applicable to all nuclei and modern spectrometers. QUANTAS is demonstrated here for (1)H and (19)F NMR, enabling heteronuclear integrals to be compared. It can be applied using fixed probe tuning, matching and pulse length, for samples with the same effective loading on the probe coil as the appropriate reference spectrum. Otherwise, an optimised tuning and matching approach is adopted for every sample together with explicit PULCON (PUlse Length-based CONcentration measurements) absolute intensity corrections.

Aortic Mycetoma From Disseminated Cunninghamella Species Infection.

Cunninghamella species are aggressive, opportunistic fungi that are becoming more commonly reported in immunocompromised patients. We present a case of disseminated Cunninghamella sp. infection after stem cell transplant for refractory multiple myeloma with formation of bilateral pleural effusions and an aortic mycetoma. PCR analysis of the patient's aortic mycetoma demonstrated a 90% match to Cunninghamella spp. This case illustrates the potential for severe opportunistic fungal infections in immunocompromised patients that can mimic other disease processes and result in an accelerated demise.

A Unique Case of Muscle-Invasive Metastatic Breast Cancer Mimicking Myositis.

Breast cancer rarely metastasizes to the muscles, and it is even more unusual for this phenomenon to result in airway compromise. We present a unique case of an 84-year-old female who presented with neck swelling and upper airway obstruction due to metastatic breast cancer invading the sternocleidomastoid muscles. After establishing the diagnosis and discussing possible treatment options, the patient elected for antiestrogen therapy, palliative tracheostomy, radiation therapy, and hospice services.

Rearrangement of a 16alpha,17alpha-Epoxy-16beta-methylandrostane-17beta-carbothioic Acid to a 17beta-Mercapto-16beta-methylandrostane-17alpha,16alpha-carbolactone.

The 16alpha,17alpha-epoxy-16beta-methylandrostane-17beta-carbothioic acid 2b rearranges in solution at ambient temperature to the 17beta-mercapto-16beta-methylandrostane-17alpha,16alpha-carbolactone 6a, possibly via the spirocyclic alpha-thiolactone 5.

A Flexible, Practical, and Stereoselective Synthesis of Enantiomerically Pure trans-5-Oxohexahydropyrrolo[3,2-b]pyrroles (Pyrrolidine-trans-lactams), a New Class of Serine Protease Inhibitors, Using Acyliminium Methodology.

A flexible, practical, and stereoselective synthesis of enantiomerically pure trans-5-oxohexahydropyrrolo[3,2-b]pyrroles (pyrrolidine-trans-lactams) is described. The key reaction involves addition of Z-ketene acetal 24 to the acyliminium ion derived from 48. This reaction is mediated by BF3·OEt2 and introduces the 6S and 6aS stereocenters stereoselectively. The acyliminium precursor was prepared in four different ways: from racemic 2,4-diaminobutyric acid 8, from (R)-asparagine, from (R)-methionine, and via a crystallization-induced dynamic resolution of a salt of the racemic amine 56. (R)-Methionine is the preferred starting material for the preparation of enantiomerically pure material. The best conditions for addition of the ketene acetal to the acyliminium ion derived from 48 were determined by systematically screening a range of ketene acetals and Lewis acids. The best ketene acetal was Z-(1-ethoxy-3-methylbut-1-enyloxyl)triisopropylsilane 24. In this series, the bulk of the silyl group of the Z-ketene acetal can be correlated with increased 6S isopropyl product. Use of the E-ketene acetal does not lead to a significant change in stereoselectivity for the 6R isopropyl product. In contrast, variation of the Lewis acid has a considerable effect on the product stereochemistry. While BF3·OEt2 gives predominantly 6S,6aS product, AlCl3 and TiCl4 give predominantly mixtures of the 6R,6aS and 6S,6aS products and TMSOTf gives 6aR material with predominantly one unknown isopropyl isomer (trans-lactam numberings used). The synthesis can conveniently be carried out on a large scale to produce multigram quantities of the trans-lactam 28, which is a key precursor of pharmacologically active molecules such as 1, a selective and orally active human neutrophil elastase inhibitor. The overall chemical yield of 1 is 1.3%, corresponding to an average of >70% yield for each of the 14 steps, and the synthesis contains only one chromatographic purification.

Investigations into the Manzamine Alkaloid Biosynthetic Hypothesis.

The biomimetic synthesis of a pentacyclic alkaloid (keramaphidin B, 1), an intermediate in the biogenetic pathway to the manzamine alkaloids, has been achieved. Compound 1 was formed by an intramolecular Diels-Alder reaction of macrocycle 2 in buffer followed by reduction with NaBH4 . This reaction provides the first direct expeimental evidence for the authors' biosynthetic hypothesis.

Solution, solid phase and computational structures of apicidin and its backbone-reduced analogs.

The recently isolated broad-spectrum antiparasitic apicidin (1) is one of the few naturally occurring cyclic tetrapeptides (CTP). Depending on the solvent, the backbone of 1 exhibits two gamma-turns (in CH(2)Cl(2)) or a beta-turn (in DMSO), differing solely in the rotation of the plane of one of the amide bonds. In the X-ray crystal structure, the peptidic C==Os and NHs are on opposite sides of the backbone plane, giving rise to infinite stacks of cyclotetrapeptides connected by three intermolecular hydrogen bonds between the backbones. Conformational searches (Amber force field) on a truncated model system of 1 confirm all three backbone conformations to be low-energy states. The previously synthesized analogs of 1 containing a reduced amide bond exhibit the same backbone conformation as 1 in DMSO, which is confirmed further by the X-ray crystal structure of a model system of the desoxy analogs of 1. This similarity helps in explaining why the desoxy analogs retain some of the antiprotozoal activities of apicidin. The backbone-reduction approach designed to facilitate the cyclization step of the acyclic precursors of the CTPs seems to retain the conformational preferences of the parent peptide backbone.

Synthesis of diverse macrocyclic peptidomimetics utilizing ring-closing metathesis and solid-phase synthesis.

The synthesis of a range of highly functionalized peptidomimetic macrocycles has been accomplished using ring-closing metathesis and enyne tandem cross-metathesis-ring-closing metathesis reactions. This approach gives access to rigidified macrocycles modeled on the structures of cyclic peptides and designed to be biologically stable. The potential for peripheral functionalization of these templates has been demonstrated using Diels-Alder reactions, palladium(0) coupling reactions, and amide formation both in the solution phase and using polymer-supported syntheses.