J. Fayos

Asteriscanolide: a sesquiterpene lactone with a new natural skeleton

Abstract A sesquiterpene lactone was isolated from the hexane extract of Asteriscus aquaticus . Its constitution and stereochemistry were determined by spectroscopic techniques, principally two-dimensional NMR correlations (COSY, HCCORR, RELAY) and with the interpretation of certain chemical transformations. The results were confirmed by X-ray diffraction and the name asteriscane is proposed for the new natural skeleton.

Structure and absolute configurations of Dictyota sp. diterpenes

Eight diterpenes belonging to the dolostane carbon skeleton have been isolated from the Canary Island brown alga Dictyola sp. The structures including absolute configuration of these diterpenes were secured by X-ray analysis of the triol derivative 7 followed by chemical interconversions.

Ribasine, a new class of papaveraceae alkaloids

Abstract The structure (including absolute stereochemistry), of ribasine, a new class of papaveraceae alkaloids with an indanobenzazepine skeleton, has been established. It was isolated from Sarcocapnos crassifolia and Corydalis claviculata .

Salvifarin, x-ray structure determination of a cis neo-clerodane diterpenoid from salvia farinacea

Abstract The structure and absolute configuration of salvifarin, a neo-clerodane diterpenoid isolated from Salvia farinacea , have been established by X-ray diffraction analysis. This result modifies the structure previously assigned to this compound.

X ray study of sesquiterpene constituents of the alga L obtusa leads to structure revision

Abstract L obtusa sesquiterpenes were subjected to an x ray analysis in orde to determine definitively the position of the Br and Cl atoms. As a result some previously-published structures 2 had to be revised.

X-ray structure determination of new brominated metabolites isolated from the red seaweed Laurencia obtusa

Abstract The structure and absolute configuration of the new sesquiterpene 1 and the bromine containing C15 nonterpenoid obtusin ( 2 ), isolated from a variety of the Canary Island red alga Laurencia obtusa were secured by X-ray crystallographic techniques.

X-ray analysis of netzahualcoyone, a triterpene Quinone methide from orthosphenia mexicana

Abstract The molecular structure and the absolute configuration of netzahualcoyone, a triterpene quinone methide with a new skeleton isolated from Orthosphenia mexicana, has been determined by X-ray analysis.

The stereochemistry of asteriscunolides: An x-ray based correction

Abstract The application of X-ray diffraction methods has shown that the configurations of Asteriscunolides A and B at the Δ9 double bond are Z, rather than those previously proposed E, while the stereochemistries of Asteriscunolides C and D were correctly established. Some unexpected NMR data and the new assignment of the spectral signals, based on 2D-NMR C H correlations and NOE-difference experiments are reported.

New compounds from . X-ray crystal and molecular structures of anamarine

Abstract The structure (including absolute stereochemistry) of olguine, an unsaturated lactone isolated from an unclassified Hyptis species, has been established by spectroscopic and X-ray analysis.

Two new polyhalogenated monoterpenes from the red alga Plocamium cartilagineum

Abstract The structures and absolute configurations of two new halogenated alicyclic monoterpenes isolated from the ether extract of the red alga Plocamium cartilagineum (Linn) Dixon were determined as: 1 R ,2 S ,4 S ,5 R -5-chloro-2- E -chlorovinyl-1,4-dibromo-1,5-dimethylcyclohexane and 1 S ,2 S ,4 R ,5 S -2-bromo-1- E -bromovinyl-4,5-dichloro-1,5-dimethylcyclohexane, respectively.