Guido W. Perold

Metabolites of proteaceae. Part VIII. The occurrence of (+)-D-allose in nature: rubropilosin and pilorubrosin from Protea rubropilosa beard

The leaves of Protea rubropilosa Beard contain (+)-D-allose in the form of the 6-O-cinnamate (rubropilosin) and the 6-O-benzoate (pilorubrosin) of 2-hydroxy-4-hydroxymethylphenyl β-D-allopyranoside. These constituents are accompanied in the plant by a β-phenylpropionate of the same glycoside.

(S)-2-hydroxycuparene [p-(1,2,2-trimethylcyclopentyl)-o-cresol] and 3,4′-ethylenebisphenol from a liverwort, Marchantia polymorpha linn

(S)-2-Hydroxycuparene and 3,4′-ethylenebisphenol have been isolated from Marchantia polymorpha Linn., together with a mixture of campesterol, stigmasterol, and β-sitosterol, and other terpenoid constituents. Syntheses of (R)-2-hydroxycuparene and of the bisphenol are reported.

Metabolites of proteaceae. Part 9. Eximin (6-O-benzoylarbutin) and the synthesis of aryl glycoside esters

Eximin, obtained from the leaves of Protea eximia(Salisb. ex Knight) Fourcade is shown to be 6-O-benzoylarbutin, and the synthesis of its tetra-acetate from arbutin is described. A synthesis of aryl glucoside esters by glucoside formation between tetra-O-acyl-1-α-D-glucopyranosyl bromides and phenols is shown to succeed only with phenols carrying electron-withdrawing substituents. Under the same conditions phenols with electrondonating substituents promote elimination reactions leading to the corresponding glucals.

Reactions of alkyl-lithium compounds with aryl halides

Reaction of methyl-lithium with tribromophenols and with other aryl polyhalides leads directly to bi- and tri-aryl products. para-Substituents (Y) of 2,6-dibromo-4-Y-phenols promote arylation of substrates by their own lithiation products as Y becomes more electron-withdrawing. An aryne epoxide is not an intermediate in these reactions. 2,4,6-Tribromo-Z-benzenes react to form coupling products when Z can co-ordinate to an introduced ortho-lithium atom or when Z can be directly lithiated. Dimeric aggregation of the organolithium intermediates occurs so as to favour coupling to halogenated substrates. Both polar (ionic) and free-radical pathways are involved.

Synthesis and 1H n.m.r. spectroscopic analysis of some 3,7-dioxabicyclo[3.3.0]octane lignans

Within the framework of a synthetic project towards the preparation of the natural germination inhibitor 2,6-diaryl-3,7-dipxabicyclo[3.3.0]octane, several molecules with the same bicyclic skeleton were prepared and their 1H n.m.r. spectra are described in detail. For the symmetrical systems particularly, the spectra exhibited second-order features and were interpreted analytically or, when necessary, by computer simulation. These n.m.r. data enabled a conformational analysis of the ring system.

Metabolites of proteaceae. Part VII. Lacticolorin, a phenolic glucoside ester, and other metabolites of Protea lacticolor Salisb.

Lacticolorin, from the leaves of Protea lacticolor Salisb., is shown to be 2-hydroxy-4-hydroxymethylphenyl 6-O-benzoyl-β-D-glucopyranoside. It is accompanied in the plant by benzoic, p-hydroxybenzoic, vanillic, and protocatechuic acids, as well as by 3,4-dihydroxybenzyl alcohol.