Lignans in seeds of Linum species.

Mature seeds of 20 Linum species were analyzed for their content of lignans. The seeds of common flax (Linum usitatissimum L.) are known to contain as characteristic lignan sesoisolariciresinol diglucoside (SDG), whose presence in seeds of some other Linum species has also been reported.

Lignans in flowering aerial parts of Linum species--chemodiversity in the light of systematics and phylogeny.

The aerial parts of 54 accessions representing 41 Linum species and four species of related genera were analysed for lignans by means of HPLC-ESI/MS-MS-UV/DAD. In total, 64 different lignans of the aryltetralin-, arylnaphthalene-, aryldihydronaphthalene-, dibenzylbutyrolactone-, and furofuran type were identified. According to their lignan profile, the Linum species can be divided in two groups accumulating as major lignan types either cyclolignans of the aryltetralin-series on one hand, or aryldihydronaphthalenes/arylnaphthalenes, on the other.

Pinoresinol-lariciresinol reductases with opposite enantiospecificity determine the enantiomeric composition of lignans in the different organs of Linum usitatissimum L.

Lignans in higher plants represent an ideal class of natural products to be investigated for the origin of stereochemical diversity since chiral lignans occur in pure enantiomeric form as well as in enantiomeric mixtures. Seeds of Linum usitatissimum contain 8S, 8'S-(+)- and 8R, 8'R-(-)-secoisolariciresinol [SS-(+)- and RR-(-)-secoisolariciresinol, respectively] as diglucosides (SS- and RR-secoisolariciresinol diglucosides) whereas aerial parts of flowering L. usitatissimum accumulate only lignans derived from RR-(-)-secoisolariciresinol.

6-methoxypodophyllotoxin-7-O-n-hexanoate, a new aryltetralin lignan ester from seeds of Linum flavum.

A new aryltetralin-type lignan, 6-methoxypodophyllotoxin-7- O-n-hexanoate, was isolated from the seeds of Linum flavum L. var. compactum (Linaceae) by silica gel column chromatography of the dichloromethane extract.

New insights into the geometry of resorc[4]arenes: solvent-mediated supramolecular conformational and chiroptical control.

The conformations of inherently chiral resorc[4]arenes were studied by circular dichroism (CD) spectroscopy. Whereas in aprotic solvents the crown conformation (C4) is preferred, protic solvents favor the boat conformation (C2). As a result of electronic coupling of the lowest L(b) state of the resorcinol unit in the resorc[4]arene, the CD spectra show a strong dependence on the conformation of the macrocycle.

Chiral discrimination on the host-guest-complexation of resorc[4]arenes with quarternary amines.

The interaction of inherently chiral resorc[4]arenes with different chiral ammonium ions was measured by ESI-MS. For that purpose one enantiomer of the ammonium guests was labeled with deuterium to distinguish the enantiomers by their mass. We synthesized the ammonium salts by reaction of chiral primary amines with either CH3I or CD3I and analyzed the resulting ammonium iodides by NMR and optical rotation.