Hugo Wyler

Pelargonidin 3-malonylsophoroside from the red Iceland poppy, Papaver nudicaule

Abstract Pelargonidin 3-malonylsophoroside was characterized as a flower pigment in a red form of the Iceland poppy, Papaver nudicaule.

Euferol and melliferol: two novel triterpenoids from Euphorbia mellifera

The structures and stereochemistries of two novel skeletons euferol [19(10→9)abeo-8α,9β,10α-tirucall-5-en-3β-ol] and melliferol [19(10→9)abeo-5α,8α,9β-tirucall-1 (10)-en-3β-ol], found in Euphorbia mellifera, have been established from spectral data and single crystal X-ray analyses.

The secodopas, natural pigments in Hygrocybe conica and Amanita muscaria

Abstract 2,3- and 4,5-Secodopas were shown to be present in small concentrations in extracts from the coloured peels of Amanita muscaria and Hygrocybe conica . They were identified by HPLC by direct comparison with a mixture of authentic samples generated enzymatically from dopa. Confirmation of the identity of these products was provided by their conversion to their cyclized successors muscaflayin and betalamic acid.

Neobetanin: A new natural plant constituent?

Abstract Neobetanin, recently reported as a natural constituent of beetroot, is not present in fresh beet juice and hence appears to be an artifact of the isolation process.

Hetero-Diels-Alder Cycloadditions ofα,β-Unsaturated Acyl Cyanides, Part 4, Substituent Effects in Reactions withp-Substituted Styrenes

Cycloadditions of α,β-unsaturated acyl cyanides (=2-oxonitriles) 1 – 6 to styrene and its p-substituted derivatives 7a – f,h are of inverse electron demand and provide, under mild conditions, regio- and stereoselectively 2-aryl-3,4-dihydro-2H-pyran-6-carbonitriles 8 – 13, generally in good yield. Rates for the cycloaddition of acryloyl cyanide 1 to p-substituted styrenes, determined in competition reactions of substrate pairs relative to that of styrene, increase in the order of electron-donating ability NO2<Cl<H<AcO<Me<AcNH<MeO of the p-substituent. Linear correlation of log (kX/kH), and σp+ substituent constants (a Hammett-type plot), gives a reaction constant ρp+ of −1.47±0.17, supporting a concerted mechanism.