Steviosid aus Süßkraut

The diterpene glycoside stevioside is the most abundant among a group of sweet steviol glycosides, present in sweetleaf (Stevia rebaudiana), which is naturally occurring in Paraguay. It has already been used by the Guarani Indians as a sweetener. Since 2011 such “steviosides” have an EU approval as sweeteners E 960. They taste ca. 250 times sweeter than sucrose. Meanwhile, they have got a significant recognition, not least due to their use in Coca Cola life®. We describe the isolation of stevioside and rebaudioside A from dried leaves of the sweetleaf plant. The complete set of spectra for stevioside is reported. Based on students' laboratory work this project is a follow up of the book “Classics in Spectroscopy” by S. Berger und D. Sicker (Wiley‐VCH 2009).     

Eucalyptol aus Eukalyptusöl

Eucalyptol (1,8‐cineol), a cyclic monoterpenoid ether, is the dominant portion of eucalyptus oil, an essential oil of Eucalyptus globulus, accessible by steam distillation of its leaves. Some herbs and spices such as basil and cardamom also contain it as characterising flavour compound. Eucalyptus is a very diverse genus of Myrtaceae naturally occurring in Australia to whom the species have adapted in evolution. Planting Eucalyptus trees outside Australia has both benefits for poor populations and drawbacks. Especially, the enormous water consumption has been criticized. The total impact is doubtful. Eucalyptol is used in flavorings, fragrances, confectionery, cosmetics, cough suppressants, and insect repellents. Higher than normal doses are a hazard. A convenient isolation of eucalyptol from eucalyptus is reported. All analytical spectra were recorded and are reproduced and interpreted either in the main part or in the supporting information. The project is a follow up of the recent book “Classics in Spectroscopy” by S. Berger und D. Sicker (Wiley‐VCH 2009).     

Diosgenin aus Yams als Hormonvorstufe

Diosgenin as a sapogenin is the aglycone of the saponine dioscin. It is occuring in plants such as yam, from which it is isolated on industrial scale since the 1940ies. Plant diosgenin is a starting substance for the synthesis of human, i.e. animal, hormones and “the pill”, which as a hormonal contraception represents a revolution in the control of human sexuality. History, isolation and spectroscopy of this complex sapogenin are reported. This article extends the briskly discussed feature “50 years pill in Germany” (Streller & Roth, ChiuZ, 2011 [( 1 ) ]) by a particular compound example. It belongs to the series on isolation and spectroscopy of natural products in this journal.     

Die konstitution des kirrothricins

Oxidation of the antibiotic kiriothricin with sodium metaperiodate gave several main degredation products ($\text{1}$, $\text{2}$, $\text{4}$). Interpretation of the spectral data of these compounds will lead to the constitution of kirrothricin ($\text{3}$).     

Quantum chemical study of solvent and substituent effects on the 1,5-hydride shift in 2,6-dimethyl-2-heptyl cations

The mechanism of the degenerate 1,5-hydride shift in 2,6-dimethyl-2-heptyl cations has been investigated using ab initio MP2 and density functional theory (DFT) hybrid (B3LYP) calculations. The potential-energy profile for the 1,5-hydride shift consists of three minima corresponding to two equivalent acyclic carbocations and one symmetrically mu-hydrido-bridged carbocation, while two equivalent unsymmetrically hydrido-bridged carbocations were located as transition-state structures. The calculated relative energy differences between acyclic carbocations and symmetrically mu-hydrido-bridged structure are significantly affected by introduction of alkyl and (CH2)n-substituents at the C4 position of the 2,6-dimethyl-2-heptyl cation structure. DFT self-consistent isodensity polarizable continuum method (SCI-PCM) and MP2 PCM continuum methods have been used to calculate the effect of solvation on geometries and relative energies of the species involved in the 1,5-hydride shift. It is found that relative energies of acyclic and mu-hydrido-bridged carbocation structures as well as the energy barriers for 1,5-hydride shifts are in accord with experimental data if solvation effects are taken into account.     

Raffinose + Raffinase = Raffinade: Raffiniert!

Raffinose has been obtained by extraction with 50% ethanol from the seeds of the Sweet Blue Lupine and purified first via a Cation exchange column and finally by analytical HPLC using a RI‐detector. All analytical spectra were recorded and are reproduced either in the main part or in the supporting information. The NMR‐ and mass‐spectra have been interpreted and compared with theoretical calculations of the ¹³C chemical shifts. The project is a follow up of the recent book “Classics in Spectroscopy” by S. Berger und D. Sicker (Wiley‐VCH 2009).     

Über Rosmarin und Rosmarinsäure

Rosmarinic acid, a tan from Lamiaceae, is found in rosemary and many other plants such as thyme, painted nettle, savory, sage, oregano, or lemon balm, from which it has been isolated here. It is a caffeic acid ester and a chiral, aromatic natural product. Rosmarinic acid tastes bitter, which may be attractive for rosemary as spice. Due to the catechol subunit the acid is an antioxidant. Using rosmarinic acid as a cure is possible due to manyfold physiological effects which are still under investigation. The rosmarinic acid biosynthesis pathway was completely elucidated at the painted nettle. This led to attempts to produce the acid biotechnologically by plant cell cultures in high yields. The preparation of a spectroscopically pure sample is challenging. All analytical spectra were recorded and are reproduced and interpreted either in the main part or in the supporting information.