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The polyacetylene contents of one form of the species Dahlia coccinea Cav. var. coccinea and also of a horticultural form derived from the same species have been examined. The nineteen polyacetylenes detected comprised eight C13, eight C14, and three C17 compounds. Five of them were previously unknown; their isolation, characterisation, and structure determination are described. They are the C14 2,3-disbustituted tetrahydroprans CH3·[CC]3·CH[graphic omitted]CH·[graphic omitted] and CH3·CH[graphic omitted]CH·[CC]2·CH[graphic omitted]CH·[graphic omitted] (R = H or Ac), and the C17 acetate CH3·CH[graphic omitted]CH·[CC]2·[CH[graphic omitted]CH]2·CH(OAc)·[CH2]3·CHCH2.

Methyl crepenynate has been synthesised from non-3-yn-1-yl-triphenylphosphonium bromide (obtained from hept-1-yne via non-3-yn-1-ol and 1-bromonon-3-yne) and the C9 aldehyde-ester with butyl-lithiumin ether, and from it crepenynic acid was obtained by alkaline hydrolysis.

Seven C10 polyacetylenes were isolated from Lactuca plumieriGren. and Godr. Dec-1-ene-4,6,8-triyn-3-one 1-hydroxydeca-4,6,8-triyn-3-one, (R)-deca-4,6,8-triyne-1,3-diol, and (R)-trans-1-(3-hydroxy-2-tetrahydro-furylidene)-hexa-2,4-diyne are new compounds and synthetic deca-4,6,8-triyn-1-ol is known. Dehydromatricarianol and its aldehyde are known natural products as also is heptadeca-8,10,16-triyne, now isolated from the garden lettuce, L. sativaL. These are the first polyacetylenes to be found in the Liguliflorae.

The isolation and determination of the structure of the fungitoxic principle of the broad bean, Vicia faba L., is described. The natural material is the acetylenic keto-ester R[graphic omitted]·CH[graphic omitted]CH·CO2Me (R =cis-EtCH:CH·C⋮C·CO), contaminated with about 2% of the more saturated ketone (R = BuC⋮C·CO). In addition, the alcohol (R =cis-EtCH:CH·C⋮C·CHOH) was found in the shoot extract. These compounds, as well as the lower homologue (R =cis-MeCH:CH·C⋮C·CO), its trans-isomer, the aldehyde (R = OCH·C⋮C), the alcohol (R = HO·CH2·C⋮C), and the close thiophen analogue MeCH[graphic omitted]CH·C⋮C·CO·[graphic omitted]·CH[graphic omitted]CH·CO2Me were synthesised, and their fungitoxic properties were compared.

Hexa-2,4-diynal, octa-2,4-diynal, and octa-2,4,6-triynal (R[CC]n·CHO) dimerise in concentrated solution with evolution of carbon monoxide, to give products of the type R[CC]n– 1·CHC(CHO)·[CC]nR; above 100° even phenylpropargyl aldehyde reacts analogously. Both geometrical isomers of the ‘dimers’ were detected and characterised.

Labelled diethyl malonate, methyl oleate, methyl linoleate, and methyl crepenynate (CH3·[CH2]4·CC·CH2·CHCH·[CH2]7·CO2Me) were all incorporated into the triol CH3·CH2·CH(OH)·[CC]2·CH(OH)·CH2·OH by cultures of the fungus in the expected manner. Specifically labelled (14C and 3H) lachnophyllum ester (CH3·CH2·CH2·[CC]2·CHCH·CO2Me) has been synthesised and also shown to be a precursor of the triol.A new metabolite, CH3[graphic omitted]CH·[CC]2·CH2·CH2·OH, has been isolated.

The structure of the polyacetylenic keto-aldehyde {H2CCH·CO·[CC]2·CH2·CH[graphic omitted]CH·[CH2]7·CHO} has been determined. It is the first C18 polyacetylene to be isolated from a plant (Pastinaca sativa L.) of the main polyacetylene-producing families. Its occurrence almost certainly establishes the derivation of the C17 falcarinone and related compounds and is in harmony with Bu'Lock's hypothesis for the biogenesis of the natural acetylenes.

Polyacetylenes occur widely in the plant family Campanulaceae. From Campanula glomerata L. 9-(tetrahydropyran-2-yl)-nona-trans,trans-2,8-diene-4,6-diyn-1-ol and 9-(tetrahydropyran-2-yl)-non-trans-8-ene-4,6-diyn-1-ol have been isolated and their structures confirmed by synthesis.

Both [1-14C]- and [2-14C]-acetate have been fed to Dahlia plants and the radioactive benzenoid polyacetylene Ph·[CC]2·CHCHMe isolated. Its selective degradation revealed a uniform labelling of alternate carbon atoms in the side-chain with the terminal methyl group derived from the methyl group of acetate and a benzene ring activity which, although not located, also agrees with an alternating labelling of its carbon atoms.Chodkiewicz coupling has been used to improve the syntheses of the cis- and trans-isomers of the phenyl-heptenediyne and osmium tetroxide oxidation to convert them into the erythro- and threo-isomers of the diol Ph·[CC]2·CH(OH)·CHMe·OH.

The hydrocarbon trans-Ph·[CC]2·CHCHMe (tritium-labelled in the benzene ring) was inserted into the tuberous roots of two Dahlia hybrids and found to be converted into the ω-alcohol trans-Ph·[CC]2·CHCH·CH2·OH, the threo-diol Ph·[CC]2·CH(OH)·CHMe·OH, and the threo-triol Ph·[CC]2·CH(OH)·CH(OH)·CH2·OH, but not into the hydrocarbon Ph·[CC]3·Me. The diol and triol had not previously been recognised as natural products.