Helmut Duddeck

Iridoid glycosides from Linaria species

Abstract The iridoid composition of four Liniria species has been investigated. Two new iridoids along with known compounds were isolated and identified. The new iridoid glucoside, 7,8-epi-antirrinoside, found in L. dalmatica, is the first iridoid glucoside with an α-orientation of the 7,8-epoxide ring, while 6β-hydroxyantirride, found in L. genistifolia and L. peloponnesiaca, appears as a second representative of the rare antirride iridoid type. Antirride was found for the first time in L. simplex. Structure elucidations were carried out mainly by spectral methods and molecular mechanics calculations. Chemosystematic relationships are also discussed.

Antimicrobial activity and cytotoxicity of Carthamus lanatus.

Total dichloromethane, methanol and water extracts, their fractions as well as volatiles of Carthamus lanatus aerial parts were phytochemically screened and evaluated for antibacterial, antifungal and cytotoxic activity. The H(2)O/MeOH fraction of the CH(2)Cl(2) extract exhibited noticeable antibacterial activity. The same fraction and the volatiles showed significant cytotoxic activity.

Antiinflammatory and analgesic effects of Carthamus lanatus aerial parts

Fractions of methanol, dichloromethane, water extracts and volatiles of Carthamus lanatus aerial parts given by oral route at a dose of 2 mg/kg showed significant antiinflammatory activities in rats. On the contrary, only the water fraction of MeOH extract possesses a significant analgesic activity.

Study of the conformational equilibria of some 2-(2′-hydroxyphenyl)-4-aryl-3H-1,5-benzodiazepines using1H,13C, and15N NMR spectroscopy

SummaryVariable temperature1H NMR experiments of 2-(2′-hydroxyphenyl)-4-phenyl-3H-1,5-benzodiazepine (5a) and its derivatives5d and5e were carried out in order to investigate the conformational behaviour of these compounds. The ΔG* values for the ring inversion barriers of5a and5d areca. 52 kJ/mol,i.e. they do not differ significantly as compared to analogous compounds without phenolic OH group(s). This indicates that the hydrogen bond has not to be opened during the inversion process. In5e the barrier is about 2–3 kJ/mol higher which can be explained by steric interference between the additional methoxy group and the H-3 atoms during ring inversion.15N NMR data which can be discussed in terms of hydrogen bond strength support this interpretation.ZusammenfassungEs wurden1H-NMR-Experimente mit 2-(2′-Hydroxyphenyl)-4-aryl-3H-1,5-benzodiazepin (5a) und seinen Derivaten5d und5e bei unterschiedlichen Temperaturen durchgeführt. Die ΔG*-Werte für die Ring-Inversion von5a und5d betragenca. 52 kJ/mol, d.h. sie sind gegenüber Verbindungen ohne eine phenolische OH-Gruppe kaum verändert. Das zeigt an, daß die Wasserstoffbrückenbindung während der Inversion nicht geöffnet werden muß. In5e ist die Barriere um ungefähr 2–3 kJ/mol höher, was durch eine sterische Wechselwirkung zwischen der zusätzlichen Methoxygruppe und den H-3-Atomen während der Inversion erklärt werden kann.15N-NMR-Daten können als Hinweise auf die Stärke der Wasserstoffbrückenbindung interpretiert werden.

Cis-Diastereoselectivity in Pictet–Spengler Reactions of L-Tryptophan and Electronic Circular Dichroism Studies

The diastereoselective synthesis of optically active 1,3-disubstituted tetrahydro-β-carbolines using polar protic Pictet-Spengler cyclization of (S)-tryptophan methyl ester with five aldehydes RCHO (R═CH(3), C(2)H(5), C(3)H(7), C(4)H(9), and C(6)H(5)) was studied. As an alternate route, the cyclization of (S)-tryptophan with the same aldehydes and subsequent methylation of the resulting tetrahydro-β-carboline carboxylic acids were also performed for comparison. (13)C NMR and electronic circular dichroism (ECD) studies and time-dependent density functional theory ECD calculations data established the relative 1,3 cis/trans and the absolute configuration (1S,3S/ 1R,3S) of the synthesized compounds. The solid-state and solution ECD study of the prepared compounds, supported by ECD calculation and X-ray data, afforded a reliable ECD method for the configurational assignment of 1,3-disubstituted tetrahydro-β-carbolines and revealed the stereochemical factors that determine the characteristic ECD data.

An Unexpected Synthesis of Novel Oxygen-Bridged 1,5-Benzothiazepine Derivatives and their Reductive Five-Membered-Ring Opening

Summary. A convenient procedure is reported for the preparation of benzofuro-annelated 2-phenyl-1,5-benzothiazepine derivatives by oxidative cyclocondensation of phenolic β-diketones with o-aminothiophenol in DMSO. The regiochemistry of these compounds is proven by HMBC signals and the existence of a five-bond 19F,13C-2 coupling. Surprisingly, treatment with LiAlH4 at room temperature led to a double reduction under opening of the five-membered ring. Refluxing such solutions with a higher amount of LiAlH4 gave rise to a further reduced derivative possessing the trans-configuration. All structures (regio- and stereochemistry) were assigned on the basis of NMR spectroscopic data.

A surprising eight-membered ring synthesis leading to enantiomerically pure tricyclic benzodiazepine derivatives

Abstract The synthesis of the title compounds 2 – 4 from naturally occurring ( R )-(+)-pulegone and o -phenylene diamines is described. Extensive NMR investigations prove that an eight-membered ring has been formed adopting a crown-type conformation.

Composition of the Essential Oil of Achillea Asplenifolia Vent. from Bulgaria

Abstract The essential oil composition of Achillea asplenifolia Vent. flower heads of Bulgarian origin is analysed by GC and GC-MS. The main constituents of the oil were chamazulene (25.6%), β-pinene (21.4%), sabinene (15.9%), and β-caryophyllene (11.3%). Antimicrobial activity tests against Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Proteus vulgaris and Candida albicans revealed significant bacteriacidal and fungicidal effects against S. aureus, C. albicans respectively and weaker against E. coli.