The title compound, [Hf(C5H5)2(C8H16)], proves a structural motif of hafna-cyclo-pentane besides the coordination of two cyclo-penta-dienyl ligands in an η(5)-fashion. The hafna-cyclo-pentane ring has a twist conformation and is substituted by two ethyl groups in the β,β'-positions, which are trans orientated to each other. One cyclo-penta-dienyl ring and one ethyl group are each disordered ove...

Hystidyl-proline [cyclo(His-Pro)] is an endogenous cyclic dipeptide produced by the cleavage of thyrotropin releasing hormone. Previous studies have shown that cyclo(His-Pro) protects against oxidative stress, although the underlying mechanism has remained elusive. Here, we addressed this issue and found that cyclo(His-Pro) triggered nuclear accumulation of NF-E2-related factor-2 (Nrf2), a tran...

Actinobacteria are well known for their potential in biotechnology and their production of metabolites of interest. Lichens are a promising source of new bacterial strains, especially Actinobacteria, which afford a broad chemical diversity. In this context, the culture medium of the actinobacterium Nocardia ignorata, isolated from the terrestrial lichen Collema auriforme, was studied. The strai...

The tripeptide pyro-Glu-His-Pro-NH2[thyrotropin-releasing hormone (TRH)] was isolated from the hypothalamus as a thyrotropin-releasing factor. It has a broad spectrum of central nervous system-mediated actions, including the stimulation of exocrine pancreatic secretion. TRH is also synthesized in the endocrine pancreas and found in the systemic circulation. Enzymatic degradation of TRH in vivo ...

The title compound, C(14)H(18)N(2)O, was synthesized by the reaction of cyclo-hexa-none and 2-amino-5-methyl-benzonitrile. In the mol-ecule, the cyclo-hexane ring displays a chair conformation, whereas the 1,3-diaza-cyclo-hexane moiety of the bicyclic system has a sofa conformation with the spiro C atom displaced by 0.603 (2) Å from the rest of the atoms of the 1,3-diaza-cyclo-hexane ring [plan...

The title compound, C(7)H(14)O(2), is a vicinal diol derived from cyclo-heptane with cis-orientated hydr-oxy groups. The mol-ecules shows no non-crystallographic symmetry. The O-C-C-O torsion angles of both mol-ecules present in the asymmetric unit [-66.4 (2) and -66.9 (2)°] are similar to those in trans-configured cyclo-hexane derivatives (including pyran-oses) as well as rac-trans-cyclo-hepta...

The title compound, C20H28O3, known as 'trichodermaerin' [systematic name: (4E)-4,9,15,16,16-penta-methyl-6-oxa-tetra-cyclo-[10.3.1.0(1,10).0(5,9)]hexa-dec-4-ene-7,13-dione], is a diterpene lactone which was isolated from Trichoderma asperellum. The structure has a tetra-cycic 6-5-7-5 ring system, with the cyclo-hexa-none ring adopting a twisted half-chair conformation and the cyclo-pentane rin...

The structures of the diastereomer diketopiperazine dipeptides cyclo(LTyr-LPhe) and cyclo-(DTyr-LPhe) are studied in gas phase using resonance-enhanced two-photon ionization, IR/UV double resonance spectroscopy quantum chemical calculation. Both diastereomers exhibit two conformations, with tyrosine ring folded over DKP phenylalanine extended outwards, or vice versa. differ only slightly by nat...