Youval Shvo

Hashish. I. The structure of cannabidiol.

Abstract Cannabidiol, one of the major components of hashish, has been shown to possess structure IIIa.

Terpenoids—II : The nuclear magnetic resonance spectra of tetracyclic triterpenes☆☆☆

Abstract The methyl region in the NMR spectra of euphane and isoeuphane derivatives have been studied. Several signals were compared with data of other triterpenes of the dammarane and lupane series.

Terpenoids—IV : The nuclear magnetic resonance study of methyl group signals in the cucurbitanes

Abstract The methyl group region in the NMR spectra of several cucurbitane derivatives have been studied.

Terpenoids—I : Oxidation of ring a in euphol☆

Abstract Euphadiene-3-one was autoxidized in potassium-t-butoxide to yield 2-hydroxy-1,8,24-euphatriene-3-one (diosphenol IIa) and 1-hydroxy-2-oxa-euphadiene-3-one (lactol IIIa) which was reduced to the δ-lactone IV and the hemiacetal Va. Hydrogenation and acetylation of the diosphenol IIa as well as hydrogenation of the diosphenol acetate IIb yielded the same 3-acetoxy-euphene-2-one VIIb. Direct acetoxylation of euphene-3-one formed 2α-acetoxy-euphene-3-one. From the autoxidation, the anhydride IX was isolated and characterized by synthesis.

Sol–gel glass with enantioselective catalytic activity

Cyclo[-(S)-phenylalanyl-(S)-histidyl] entrapped in a silicon based sol–gel glass matrix induces catalytic hydrocyanation of benzaldehyde to (R)-mandelonitrile with e.e. ≥ 94%.

Dimethyl (dimethylaminomethylene)malonate: crystal structure and dynamic behaviour in solution

The structure of the title compound (I) was determined from photographic X-ray data. Crystals are monoclinic, space group P21/a, with Z= 4 in a unit cell of dimensions: a= 6·200 ± 0·002, b= 12·144 ± 0·002, c= 12·859 ± 0·002 A, and β= 86·41 ± 0·04°. The structure was solved by direct methods and refined by full-matrix least-squares techniques to R 0·055 for 867 observed reflections.The molecule consists of two essentially planar parts: the trans-dimethylaminoacrylate portion, and the remaining methoxycarbonyl group. The nitrogen atom is coplanar with its bonded neighbours. The bond lengths of the group N·C:C are N–C 1·337 and CC, 1·380 A, indicating extensive delocalisation. Comparison with i.r. results suggests a similarity of the conformations of (I) in the crystalline and liquid phases, and enables the ΔG* value for isomerisation about the CC bond in the similarly delocalised methyl trans-3-dimethylaminoacrylate to be estimated as 30·8 kcal mol–1. The lower value for (I), 15·6 kcal mol–1, cannot be ascribed to its ground-state delocalisation and should be attributed mainly to a stabilisation of the dipolar transition-state.

Reaction between an azabullvalene and nonacarbonyldi-iron

The reaction between 3-methoxy-4-azatricyclo-[3,3,2,02,8]deca-3,6,9-triene and Fe2(CO)9 gives a novel σ–π-allyl heterocyclic tricarbonyliron complex (III) and methoxycarbonylcyclo-octatetraenetricarbonyliron complex (IV).