Application of Crystalline Matrices for the Structural Determination of Organic Molecules.

While single-crystal X-ray diffraction (SC-XRD) is one of the most powerful structural determination techniques for organic molecules, the requirement of obtaining a suitable crystal for analysis limits its applicability, particularly for liquids and amorphous solids. The emergent use of porous crystalline matrices that can absorb organic compounds and stabilize them via host-guest interactions for observation via SC-XRD offers a way to overcome this hindrance. A topical and current discussion of SC-XRD in organic chemistry and the use of preformed matrices for the analysis of organic compounds, with a particular focus on the absolute structure determination of chiral molecules, is presented.

A conserved coccidian gene is involved in Toxoplasma sensitivity to the anti-apicomplexan compound, tartrolon E.

New treatments for the diseases caused by apicomplexans are needed. Recently, we determined that tartrolon E (trtE), a secondary metabolite derived from a shipworm symbiotic bacterium, has broad-spectrum anti-apicomplexan parasite activity. TrtE inhibits apicomplexans at nM concentrations in vitro, including Cryptosporidium parvum, Toxoplasma gondii, Sarcocystis neurona, Plasmodium falciparum, Babesia spp.

A symbiotic bacterium of shipworms produces a compound with broad spectrum anti-apicomplexan activity.

Apicomplexan parasites cause severe disease in both humans and their domesticated animals. Since these parasites readily develop drug resistance, development of new, effective drugs to treat infection caused by these parasites is an ongoing challenge for the medical and veterinary communities. We hypothesized that invertebrate-bacterial symbioses might be a rich source of anti-apicomplexan compounds because invertebrates are susceptible to infections with gregarines, parasites that are ancestral to all apicomplexans.

GABA-modulating bacteria of the human gut microbiota.

The gut microbiota affects many important host functions, including the immune response and the nervous system. However, while substantial progress has been made in growing diverse microorganisms of the microbiota, 23-65% of species residing in the human gut remain uncultured, which is an obstacle for understanding their biological roles. A likely reason for this unculturability is the absence in artificial media of key growth factors that are provided by neighbouring bacteria in situ.

Tundrenone: An Atypical Secondary Metabolite from Bacteria with Highly Restricted Primary Metabolism.

Methane-oxidizing bacteria, aerobes that utilize methane as their sole carbon and energy source, are being increasingly studied for their environmentally significant ability to remove methane from the atmosphere. Their genomes indicate that they also have a robust and unusual secondary metabolism. Bioinformatic analysis of the Methylobacter tundripaludum genome identified biosynthetic gene clusters for several intriguing metabolites, and this report discloses the structural and genetic characterization of tundrenone, one of these metabolites.

The Crystalline Sponge Method: A Solvent-Based Strategy to Facilitate Noncovalent Ordered Trapping of Solid and Liquid Organic Compounds.

A strategy that leverages solvent effects to noncovalently trap solid and unstable liquid organic compounds within a crystalline sponge ({[(ZnI)(tris(4-pyridyl)-1,3,5-triazine)]·(CHCl)}) in a simple, mild, and efficient fashion for target molecule structure determination via X-ray diffraction is disclosed. Host-guest structures were obtained using third-generation synchrotron radiation, and new beamline hardware allowed rapid data collection in ~5-24 minutes. This is 40-90% faster than previously reported crystalline sponge synchrotron datasets collected by us, and approximately a 150-720-fold decrease in time versus using a typical in-house diffractometer, effectively enabling the potential for high-throughput analysis.

Macrotermycins A-D, Glycosylated Macrolactams from a Termite-Associated Amycolatopsis sp. M39.

Bioassay-guided metabolomic analyses led to the characterization of four new 20-membered glycosylated polyketide macrolactams, macrotermycins A-D, from a termite-associated actinomycete, Amycolatopsis sp. M39. M39's sequenced genome revealed the macrotermycin's putative biosynthetic gene cluster.

Homodimericin A: A Complex Hexacyclic Fungal Metabolite.

Microbes sense and respond to their environment with small molecules, and discovering these molecules and identifying their functions informs chemistry, biology, and medicine. As part of a study of molecular exchanges between termite-associated actinobacteria and pathogenic fungi, we uncovered a remarkable fungal metabolite, homodimericin A, which is strongly upregulated by the bacterial metabolite bafilomycin C1. Homodimericin A is a hexacyclic polyketide with a carbon backbone containing eight contiguous stereogenic carbons in a C20 hexacyclic core.

Variable genetic architectures produce virtually identical molecules in bacterial symbionts of fungus-growing ants.

Small molecules produced by Actinobacteria have played a prominent role in both drug discovery and organic chemistry. As part of a larger study of the actinobacterial symbionts of fungus-growing ants, we discovered a small family of three previously unreported piperazic acid-containing cyclic depsipeptides, gerumycins A-C. The gerumycins are slightly smaller versions of dentigerumycin, a cyclic depsipeptide that selectively inhibits a common fungal pathogen, Escovopsis.

Small-Molecule Reactivation of Mutant p53 to Wild-Type-like p53 through the p53-Hsp40 Regulatory Axis.

TP53 is the most frequently mutated gene in human cancer, and small-molecule reactivation of mutant p53 function represents an important anticancer strategy. A cell-based, high-throughput small-molecule screen identified chetomin (CTM) as a mutant p53 R175H reactivator. CTM enabled p53 to transactivate target genes, restored MDM2 negative regulation, and selectively inhibited the growth of cancer cells harboring mutant p53 R175H in vitro and in vivo.

Identification of a Dual Inhibitor of Janus Kinase 2 (JAK2) and p70 Ribosomal S6 Kinase1 (S6K1) Pathways.

Bioactive phytochemicals can suppress the growth of malignant cells, and investigation of the mechanisms responsible can assist in the identification of novel therapeutic strategies for cancer therapy. Ginger has been reported to exhibit potent anti-cancer effects, although previous reports have often focused on a narrow range of specific compounds. Through a direct comparison of various ginger compounds, we determined that gingerenone A selectively kills cancer cells while exhibiting minimal toxicity toward normal cells.

The crystalline sponge method: MOF terminal ligand effects.

Bromide and chloride analogs of the commonly used zinc iodide-based metal organic framework for the crystalline sponge method were synthesized and evaluated. Inclusion of (1R)-(-)-menthyl acetate into these MOFs was analysed using third-generation synchrotron radiation, and the effects and potential benefits of varying the MOF terminal ligand are discussed.

Analysis of rapidly synthesized guest-filled porous complexes with synchrotron radiation: practical guidelines for the crystalline sponge method.

A detailed set of synthetic and crystallographic guidelines for the crystalline sponge method based upon the analysis of expediently synthesized crystal sponges using third-generation synchrotron radiation are reported. The procedure for the synthesis of the zinc-based metal-organic framework used in initial crystal sponge reports has been modified to yield competent crystals in 3 days instead of 2 weeks. These crystal sponges were tested on some small molecules, with two being unexpectedly difficult cases for analysis with in-house diffractometers in regard to data quality and proper space-group determination.

Natalamycin A, an Ansamycin from a Termite-Associated sp.

We report a preliminary functional and complete structural characterization of a highly unusual geldanamycin analog, natalamycin A, that was isolated from strain M56 recovered from a South African nest of termites. Bioassay-guided fractionation based on antifungal activity led to the isolation of natalamycin A, and a combination of NMR spectroscopy and X-ray crystallographic analysis, including highly-accurate quantum-chemical NMR calculations on the largest and most conformationally-flexible system to date, revealed natalamycin A's three-dimensional solid- and solution-state structure. This structure along with the structures of related compounds isolated from the same source suggest a geldanamycin-like biosynthetic pathway with unusual post-PKS modifications.

Bacterial symbionts in agricultural systems provide a strategic source for antibiotic discovery.

As increased antibiotic resistance erodes the efficacy of currently used drugs, the need for new candidates with therapeutic potential grows. Although the majority of antibiotics in clinical use originated from natural products, mostly from environmental actinomycetes, high rediscovery rates, among other factors, have diminished the enthusiasm for continued exploration of this historically important source. Several well-studied insect agricultural systems have bacterial symbionts that have evolved to produce small molecules that suppress environmental pathogens.

Mild double allylboration reactions of nitriles and acid anhydrides using potassium allyltrifluoroborate.

The double allylboration of nitriles and acid anhydrides to form bis-allyl amines and esters, respectively, can be achieved through the use of potassium allyltrifluoroborate in the presence of boron trifluoride etherate at room temperature. The method described is relatively mild, exhibits chemoselectivity to other electrophiles present, avoids the use of metals, and features the use of an operationally stable and robust potassium organotrifluoroborate reagent.

Stereocontrolled synthesis of contiguous C(sp3)-C(aryl) bonds by lanthanide(III)-catalyzed domino aryl-Claisen [3,3]-sigmatropic rearrangements.

A domino [3,3]-sigmatropic aryl-Claisen rearrangement of cyclic and acyclic bisaryloxy-substituted alkenes can be performed in high yield by using Ln(fod)(3) catalysis to obtain bisphenolic products incorporating two contiguous aryl-C(sp(3)) bonds. Stereospecific rearrangement was observed for cyclic substrates. The precursor diaryl ethers were typically synthesized from the corresponding diols by double arylation procedures using either copper catalyzed coupling of aryltrifluoroborate salts or by S(N)Ar reaction.

Cyclobutanone mimics of penicillins: effects of substitution on conformation and hemiketal stability.

The tendency for carbocyclic analogues of penicillins to undergo hydrate and hemiketal formation is central to their ability to function as beta-lactamase inhibitors. 2-Thiabicyclo[3.2.

Inverse H-C ex situ HRMAS NMR experiments for solid-phase peptide synthesis.

The growing importance of solid-phase peptide synthesis (SPPS) has necessitated the development of spectroscopic experiments that can be used to obtain structural and conformational information on resin-bound peptides. Despite the utility of two-dimensional high-resolution magic angle spinning (HRMAS) NMR experiments that provide homonuclear shift correlations, experiments that provide heteronuclear shift correlations are necessary for complex conformational and structural elucidatory problems. Here we report the optimization and implementation of non-gradient inverse NMR experiments for acquiring the 1H-13C shift correlations of resin-bound peptides.