Lilioside C,a glycerol glucoside from Lilium lancifolium

A new glycerol glucoside, lilioside C, has been isolated from the leaves and stems of Lilium lancifolium. Its structure including the configuration of the aglycone moiety has been elucidated by chemical and spectroscopic means and by its synthesis.     

Chemical studies of marine inverterbrates. XXIX 4 alpha-Methyl-3 beta 8-beta-dihydroxy-5 alpha-ergost-24(28)-en-23-one, a novel polyoxygenated sterol from the soft coral Litophyton viridis. (Coelenterata, Octocorallia, Alcyonacea).

A novel sterol, 4α-methyl-3β,8β-dihydroxy-5α-ergost-24(28)-en-23-one (I), has been isolated from the soft coral Litophyton viridis. Its structure and relative configuration has been established by X-Ray diffraction analysis.     

3,4-dihydroxy-2-hydroxymethylpyrrolidine from Arachniodes standishii

3,4-Dihydroxy-2-hydroxymethylpyrrolidine, which has not been encountered naturally before, was isolated from the Pteridophyte Arachniodes standishii. Its configuration was determined as 2,3-cis and 3,4-trans from NMR spectra.     

Acetoxonium ions from acetoxyoxiranes and orthoesters: their conversion into ethylidene acetals,rearrangement, and solvolysis

The acid-catalysed ethylidenation of some methyl pentopyranosides has been studied and the configuration at the acetal carbon atom assigned by p.m.r. spectroscopy. There is a strong preference for the isomer in which the methyl group has the endo configuration. Several cyclic alkyl orthoacetates derived from methyl pentopyranosides have been prepared by orthoester exchange and the endo C-methyl isomer shown to preponderate. Treatment of vicinal acetoxyoxiranes and orthoacetates with boron trifluoride followed by lithium borohydride, or with diborane, yields ethylidene acetals in which the C-methyl group is endo. Rearrangements of the hexachloroantimonate salts of acetoxonium ions derived from methyl lyxo- and arabino-pyranosides, possessing trans-vicinal acetoxyl groups, have been studied. The ions having the arabino configuration are preferred in both the α and β series. The reaction of cyclic orthoacetates of methyl β-L-arabinopyranoside and some derivatives with dry acetic acid proceeds via an acyclic acetoxonium ion to yield only products having the L-arabino configuration.     

Determination of the anomeric configuration of D-xylose with D-xylose isomerases.

The anomeric configuration of D-xylose, resulting from hydrolysis of β-D xylopyranosides by β-D-xylosidase from Bacillus pumilus, has been determined by an enzymic procedure, based on the stereospecificity of D-xylose isomerases. The initial hydrolysis product is α-D-xylose. β-D-Xylosidase from Bacillus pumilus thus acts by inversion of configuration in contrast to most other glycosidases.     

Desangeloylshairidin,a sesquiterpene lactone from Guillonea scabra

From the roots of Guillonea scabra a new sesquiterpene lactone has been isolated. Its structure has been established by spectroscopic means as desangeloylshairidin.     

The lachrymatory principle of Petiveria alliacea

The lachrymatory principle of Petiveria alliacea has been isolated from a fresh homogenate of the root. Its structure and geometric configuration have been determined as (Z)-thiobenzaldehyde S-oxide by means of NMR, IR, MALDI-MS and by comparison with an authentic compound obtained by synthesis. This unique compound represents only the third naturally occurring sulfine (thiocarbonyl S-oxide) to be reported. Its formation and possible subsequent rearrangements are discussed. Its antibacterial and antifungal activities are also reported.     

(+)-5,17-dehydromatrine N-oxide,a new alkaloid in Euchresta japonica

A new lupin alkaloid, (+)-5,17-dehydromatrine N-oxide, was isolated from the fresh aerial parts of Euchresta japonica. Its structure was confirmed by spectrometric data and by direct comparison with a synthetic sample, prepared from (+)-sophoranol ((+)-5-hydroxymatrine). It was also concluded that (+)-5,17-dehydromatrine N-oxide and (+)-matrine N-oxide possess the same configuration with respect to the asymmetric nitrogen by NMR spectra.     

Thermal behaviour,phase diagram,and spectroscopic properties of rac-indobufen and its enantiomers

The binary phase diagram of the enantiomers of indobufen, 1 (Ibustrin), an antithrombotic drug, has been investigated by differential scanning calorimetry (DSC); 1 is a racemic compound (racemate) with melting point lower than that of the enantiomers. Its thermal behaviour (DSC) has been examined and is discussed in comparison with other physical methods (IR spectroscopy and X-ray powder diffraction). Absolute configuration has been assigned to the enantiomers by ¹H-NMR correlations. © 1995 Wiley-Liss, Inc.     

Cordatin,a new diterpene from Aparisthmium cordatum

A new furano diterpene, cordatin, with a clerodane skeleton has been isolated from the bark of Aparisthmium cordatum. Its molecular structure has been investigated by spectroscopic means and by X-ray analysis.     

Aparisthman,methyl 1-(3-furoylmethyl)-4a-hydroxy-1,2-dimethyl-2,3,4,4a,5,8,9,9a-octahydro-1H-benzocycloheptene-6-carboxylate,a seven membered ring diterpenoid from Aparisthmium cordatum

A new diterpenoid, aparisthman, with a rearranged clerodane skeleton has been isolated from the bark of Aparisthmium cordatum. Its molecular structure has been investigated by spectroscopic means and by X-ray analysis.     

Acide nor-19 anticopalique d'Agathis lanceolata

A new diterpenoid, 19-noranticopalic acid, has been isolated from Agathis lanceolata resin. Its structure has been established by spectroscopic methods and chemical correlations with anticopalic acid.     

Enzymatic epimerization of d-erythro-dihydroneopterin triphosphate to l-threo-dihydroneopterin triphosphate

An enzyme has been discovered in Escherichia coli that catalyzes the conversion of the triphosphate ester of 2-amino-4-hydroxy-6-(d-erythro-1′,2′,3′-trihydroxypropyl)-7,8-dihydropteridine, (i.e. d-erythro-dihydroneopterin triphosphate) to an epimer of this compound, l-threo-dihydroneopterin triphophate. The enzyme, which is here named “d-erythro-dihydroneopterin triphosphate 2′-epimerase,” needs a divalent cation (Mg²⁺ or Mn²⁺ is most effective) for maximal activity. Its molecular weight is estimated at 87 000–89 000. Little or no activity can be detected if either the monophosphate or the phosphate-free form of the substrate is incubated with the enzyme. Evidence is presented to establish that all three phosphate residues of the substrate are retained in the product and that the product is of the l-threo configuration.     

Absolute configuration of the isomer of fluorocitrate that inhibits aconitase

The absolute configuration of the isomer of fluorocitrate that is a strong inhibitor and activator of aconitase has been determined to be 2R, 3R, as shown in the Fischer and perspective diagrams below.

Fischer diagram Perspective diagramThis is the isomer described by Dummel and Kun (1969, J. Biol. Chem.244, 2966) and defined as (?)-erythro-fluorocitrate by them. We report here structural studies of the mirror image (enantiomer) of this isomer. Crystals of the complex of the diethyl ester of (+)-erythro-fluorocitrate with (?)-methylbenzylamine were studied by X-ray diffraction techniques. Since the absolute configuration of (?)-methylbenzylamine has already been determined experimentally, the absolute configuration of the (+)-erythro isomer of fluorocitrate is thereby established. This isomer is shown to be noninhibitory with the enzyme aconitase, while its racemate is a powerful inhibitor. Thus it is proved that the absolute configuration of the isomer of fluorocitrate that is formed from fluoroacetyl-CoA by the enzyme citrate synthase, and that inhibits aconitase, is the 2R, 3R, isomer.     

Hygrophiloside,an iridoid glucoside from Hygrophila difformis (Acanthaceae)

A new iridoid glucoside, hygrophiloside, has been isolated from Hygrophila difformis. Hygrophiloside is apparently identical to the so-called ‘Cardanthera-Pseudoindican’. Its structure has been established by spectroscopic means and by reduction to isoaucubin.     

Arjunolitin,a triterpene glycoside fromTerminalia arjuna

Arjunolic acid diglycoside, which we have named arjunolitin, has earlier been reported fromTerminalia arjuna. Its structure has now been established as 3-O-β-d-glycopyranosyl 2α,3β-23-tri-hydroxyolean-12-en-28-oic acid 28-O-β-d-glucopyranoside by chemical and spectral data.     

R(−)-Canadaline as first secoberbine alkaloid from Corydalis cava

R(−)-Canadaline (1) is the first alkaloid from the class of secoberbines that was found in Corydalis cava. It was identified from a historical collection of substances and its genuine origin was proven. Its absolute configuration was determined by circular dichroism and comparison with published data of the S-enantiomer. Until now only the other enantiomer, S(+)-canadaline, was known to occur in Hydrastis canadensis.     

Caractérisation de la sticticine chez le lichen Lobaria laetevirens

Sticticin has been isolated from the thallus of Lobaria laetevirens. Its structure was determined by spectroscopic methods (NMR, MS) and comparison with a synthetic sample. It has been found in several species of the Stictaceae.     

Peptide alkaloids of Scutia buxifolia

Two new components, the peptide alkaloid scutianine D and scutianene C have been isolated from Scutia buxifolia and their structures elucidated. The configuration of some of the asymmetric centers of scutianine A has been determined by gas chromatography.     

Preleosibirin,a prefuranic labdane diterpene from ballota nigra subsp. foetida

From the aerial parts of Ballota nigra subsp. foetida a new prefuranic labdane diterpene, preleosibirin, has been isolated. Its structure was established by spectroscopic means and by correlation with the previously known diterpenoid leosibirin.