Microbial Hydroxylation and Simultaneous Formation of the 4''-O-Methylglucoside of the Tyrosine-Kinase Inhibitor CGP 62706

Two fungal strains of Beauveria bassiana, DSM 875 and DSM 1344, hydroxylated CGP 62706, an inhibitor of the EGF-receptor tyrosine kinase, in the C(4') position and subsequently formed the glucosylated metabolite with 5–11% and 7–15% yield, respectively. The reaction could be successfully scaled up to 3 l fermentation volume with strain DSM 875. The structure of the glycosylated compound was determined by micro-HPLC-MS and NMR after production by fermentation on the mg scale. In addition, the biotransformation also provides access to the free 4'-hydroxylated compound, as the glycoside can easily be hydrolyzed

The 3D-structure of a natural inhibitor of cell adhesion molecule expression

AbstractThe three-dimensional structure of cyclopeptolide HUN-7293, a naturally-occurring inhibitor of cell adhesion molecule expression, has been determined from nuclear magnetic resonance data recorded in solution and from X-ray diffraction analysis of single crystals. The backbone conformation of HUN-7293 is characterized by two cis-peptide bonds in both the solution and crystalline state. Differences between the solution and crystal structure are visible for the orientation of some side chains and the strength of two transannular hydrogen bonds. Such structural information helps to provide insight into the molecular architecture of HUN-7293 on the atomic level and opens the way for structure-based modifications of this novel inhibitor of cell adhesion molecule expression

Decatransin, a novel natural product inhibiting protein translocation at the Sec61/SecY translocon

A new cyclic decadepsipeptide was isolated from Chaetosphaeria tulasneorum with potent bioactivity on mammalian and yeast cells. Chemogenomic profiling in S. cerevisiae indicated that the Sec61 translocon, the machinery for protein translocation and membrane insertion at the endoplasmic reticulum, is the target. The profiles were similar to those of cyclic heptadepsipeptides of a distinct chemotype (HUN-7293/cotransin) that had previously been shown to inhibit cotranslational translocation at the mammalian Sec61 translocon. Unbiased, genome-wide mutagenesis followed by full-genome sequencing in both fungal and mammalian cells identified dominant mutations in Sec61p/Sec61α1 to confer resistance. Most, but not all, of these mutations affected inhibition by both chemotypes, despite an absence of structural similarity. Biochemical analysis confirmed inhibition of protein translocation into the endoplasmic reticulum of both co- and posttranslationally translocated substrates by both chemotypes, demonstrating a mechanism independent of a translating ribosome. Most interestingly, both chemotypes were found to also inhibit SecYEG, the bacterial Sec61 homolog. We suggest "decatransin" as the name for this novel decadepsipeptide translocation inhibitor

Cyanopeptolin 954, a Chlorine-Containing Chymotrypsin Inhibitor of Microcystis aeruginosa NIVA Cya 43

A new depsipeptide, cyanopeptolin 954 (1), was isolated from the freshwater cyanobacterium Microcystis aeruginosa NIVA Cya 43. The structure of the compound was elucidated by chemical and spectroscopic analyses, including 2D NMR and GC-MS of the hydrolysate. The major structural differences compared to previously characterized heptadepsipeptides of Microcystis are the replacement of the basic amino acid in position 4 by l-leucine, the presence of l-phenylalanine in position 6, and the uncommon residue 3 -chloro-N-Me-l-tyrosine in position 7. Cyanopeptolin 954 inhibited chymotrypsin with an IC50 value of 45 nM. Nostopeptin BN920, formerly isolated from the cyanobacterium Nostoc,1 was isolated from the same strain of Microcystis, and a cis amide bond between Phe (6) and N-Me-Tyr (7) was shown. Nostopeptin BN920 inhibited chymotrypsin with an IC50 value of 31 nM

Chemical Constituents from Gouania longipetala and Glyphaea brevis

Five compounds were isolated altogether from the two medicinal plants. Glycerol monovalerate (1), palmarumycin BG1 (2), and de-O-methyllasiodiplodin (3) were isolated from G. longipetala. Additionally, epicatechin (4) and its’ dimer procyanidin B2 (5) were isolated from the stem bark of G. brevis. Their structures were elucidated by spectroscopic experiments. 1 displayed moderate antibacterial activities with the least MIC of 125 µg/mL against E. faecalis. In addition, 1 reduced DPPH with an IC50 value of 102.34 µg/mL

Efficient synthesis of [3H]-sanglifehrin A via selective oxidation/reduction of alcohols at C31 and C35.

[Reaction: see text]. Sanglifehrin A is a novel complex natural product showing strong immunosuppressive activity and remarkably high affinity for cyclophilin A. To assess its pharmacokinetic properties in vivo, an efficient synthetic route was developed to introduce a tritium label in position C35 of sangliferin A via an oxidation/reduction strategy. The synthetic approach is particularly attractive, because the C35-oxo intermediate 7 is available in good yield on large scale and the reducing agent, lithium tri-sec-butylborotritide, is readily available. An attempt to apply a similar strategy to the alcohol in position C31 led primarily to C31-epi-hydroxy sanglifehrin A under a variety of conditions

Efficient Screening of Target-Specific Selected Compounds in Mixtures by 19F NMR Binding Assay with Predicted 19F NMR Chemical Shifts

Ligand-based 19F NMR screening is a highly effective and well-established hit-finding approach. The high sensitivity to protein binding makes it particularly suitable for fragment screening. Different criteria can be considered for generating fluorinated fragment libraries. One common strategy is to assemble a large, diverse, well-designed and characterized fragment library which is screened in mixtures, generated based on experimental 19F NMR chemical shifts. Here, we introduce a complementary knowledge-based 19F NMR screening approach, named 19Focused screening, enabling the efficient screening of putative active molecules selected by computational hit finding methodologies, in mixtures assembled and on-the-fly deconvoluted based on predicted 19F NMR chemical shifts. In this study, we developed a novel approach, named LEFshift, for 19F NMR chemical shift prediction using rooted topological fluorine torsion fingerprints in combination with a random forest machine learning method. A demonstration of this approach to a real test case is reported

A Detailed Investigation on Conformation, Permeability and PK Properties of Two Related Cyclohexapeptides

Abstract: This contribution provides detailed insights regarding permeability properties of published cyclohexapeptides related to their conformation. The study includes data on oral bioavailability and PK parameters including application of a known enhancer. Interestingly, the latter did not show an effect, neither on the cyclic peptide exhibiting low oral uptake nor on the similar molecule showing a 30 % oral bioavailability in mice. These results are discussed in the context of exposed polar surface area for the preferred conformation and structural data obtained by NMR and X-ray crystallography. Graphical Abstract: [Figure not available: see fulltext.

Quality control in combinatorial chemistry: determinations of amounts and comparison of the "purity" of LC-MS-purified samples by NMR, LC-UV and CLND.

The absolute purities of 20 purified samples from a combinatorial library have been determined by a new method that uses the DMSO sidebands [1J[13C-1H]] as an internal standard for quantification. The obtained absolute amounts are compared with the amounts of sample obtained by weighing, with the calculated weights obtained by chemiluminescent nitrogen detection (CLND) chromatography and with the relative purities obtained by LC-UV chromatography