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D Hunkler

Publications and source records attributed to D Hunkler.

5 recordsLinked to original sources
PubMed2001

Pentagonal dodecahedranes: polyfunctionalization and MS fragmentation.

With the use of four- to eight-fold functionalized dodecahedranes (1-3), opportunities to arrive at highly strained dodecahedranes with two to four pairs of vicinal, eclipsed bromine substituents through front-side substitution and addition reactions have been explored. In standard processes, the interception of beta-OCH(3) radical/cationic intermediates was not problematic (9-12, 37, 50). The interception of beta-CO(2)R radicals was possible for Cl(*) (18) but not for Br(*) (17). The interception of beta-chloro radicals was possible for Cl(*) (27) but not for Br(*) (26), and the interception of beta-Br cations ("bromonium ions") with Br(-) was modest (45) to highly inefficient (24, 26). Two X-ray structural analyses (dimethoxy dibromide 9 and tetramethoxy tetrabromide 53) indicated the structural consequences of the molecular strain introduced by the two (four) vicinal CH(3)O/Br pairs. A systematic analysis of the MS spectra confirms that, in virtually all cases studied, the elimination of the substituents occurs without significant carbon-cage disruption, leading ultimately to multiply unsaturated dodecahedral ions for dodecahedrahexa(C(20)H(8))enes, -hepta(C(20)H(6))enes, and -octa(C(20)H(4))enes.

Journal Article↗
PubMed1994

Caffeoylquinic acids and some biological activities of Pluchea symphytifolia.

From the aerial parts of Pluchea symphytifolia, four known and two new caffeoylquinic acids, 1,3,4,5-tetra-O-caffeoylquinic acid and 1,3-di-O-[3,4,-bis-(3,4-dihydroxyphenyl)-cyclobutane-1,2-dicarbonyl]- 4,5-di-O-caffeoylquinic acid, and two flavonols were isolated and their structures elucidated by mass and NMR spectroscopy and by chemical degradation. The aqueous extract had weak antibacterial and weak antisecretory effects; the lipophilic extract showed a modest anthelmintic activity. The higher caffeoylated quinic acids participated in the antibacterial and anthelmintic effect of the extracts.

Animals↗
PubMed1986

Possibilities of selective screening for inborn errors of metabolism using high-resolution 1H-FT-NMR spectrometry.

NMR spectrometry, hitherto a powerful tool in organic chemistry for elucidating the structures of chemical compounds, has been improved during recent years to become a method suitable for detection of normal and abnormal metabolites in physiologic media. We have investigated native urinary specimens from patients known to suffer from different inherited metabolic disorders using a 250 MHz FT-NMR spectrometer and were able to confirm the diagnosis in every case. Chemical shift values of a variety of appropriate metabolites, run at pH 2.5, are presented here. It is concluded, that NMR spectrometry is an excellent method with which to screen for inborn errors of metabolism provided that high-field instruments with the best available specifications are applied.

Child↗
PubMed1983

Differential response of cultured parsley cells to elicitors from two non-pathogenic strains of fungi. 1. Identification of induced products as coumarin derivatives.

Dark-grown cell suspension cultures of parsley, Petroselinum hortense, produce furanocoumarins after treatment with elicitor preparations of either Phytophthora megasperma f.sp. glycinea (Pmg elicitor) or Alternaria carthami Chowdhury (Ac elicitor). The linear furanocoumarins, psoralen and xanthotoxin, and the benzodipyrandione, graveolone, are the major products synthesized in response to Pmg elicitor, besides small amounts of the furanocoumarin bergapten. Treatment with Ac elicitor induces predominantly the formation of bergapten and the furanocoumarin isopimpinellin, as well as small amounts of graveolone. While Pmg elicitor leads to cell death within a few days, cell mass increased for at least 6 days after treatment with Ac elicitor. Brefeldin A, a phytotoxin produced by A. carthami, inhibits growth of parsley cell suspension cultures considerably at a concentration of 0.01 mM and growth of the cells ceased at a concentration of 0.1 mM toxin. Concomitantly, furanocoumarin biosynthesis was suppressed in our system by a concentration of brefeldin A within 0.01-0.1 mM.

Alternaria↗