Acetylenic compounds, naturally occurring

N. A. Sorensen Studies Related to Naturally Occurring Acetylene Compounds. IX. The Occurrence of Methyl dec-8-cis-en-4 6-diynoate (= a,/9-Dihydro-Matricaria Ester) and 2-cis 8-trans-Matricaria Ester in Nature. Acta Chem. Scand. 6, 883 (1952). 

Studies related to Naturally Occurring Acetylene Compounds. VII. The Synthesis of two Stereoisomers of Methyl n-Decadiene-2,8-diyn-4,6-oates the Configuration of Matricaria Ester. Acta Chem. Scand. 5, 1244 (1951). 

Occurring Acetylene Compounds. VIII. The Synthesis of Methyl n-Dec-2-en-4 6 8-triynoate, an Isomer of the Naturally Occurring Dehydro-matricaria Ester. Acta Chem. Scand. 6, 602 (1952). 

Studies Related to Naturally Occurring Acetylene Compounds. X. The... 

Naturally Occurring Acetylene Compounds. XX. A Preliminary Communication on Some Polyacetylenic Pigments from Compositae Plants. Acta Chem. Scand. 8, 1769 (1954). 

Some Naturally Occurring Acetylenic Compounds. Proc. Chem. Soc. 

Very many naturally occurring 3-alkyl- or 3-acylfurans are now routinely synthesized by preparing a substrate for treatment with 3-furyllithium, itself made from 3-bromofuran according to Fukuyama, Tokoroyama, and Kubota, who used it to obtain pyroangensolide and fraxinellone.212 Equally, 2-lithiofuran is used for such natural products as the acetylenic furans from Alphonsea ventricosa213 and other compounds.214 For the synthesis of the sesquiterpenoid sponge-metabolite pleraplysillin-2 78, the lithiofuran 79 and therefore the bromofuran 80 was needed to secure the orientation a suitable preparation was devised for 80.215... 

The naturally occuring thietane acetylene compounds showed in the reduced form three absorption maxima 340, 360, and 374 nm) and, in the oxidized form, four bands at 294, 306.5, 393, and 418 nm. ... 

Scheme 43 shows the details of the different steps involved in the equilibrium. The nucleophilic attack of the P(III) derivative on the acetylenic bond yields a 1,3-dipole which, after a fast protonation, frees aZ ion. If the subsequent addition of this ion occurs on the P atom (reaction a), a P(V) phosphorane is formed, but the addition of Z on the ethylenic C atom (reaction b) results in the formation of an ylide. Both of these reactions occur under kinetic control and, in both cases, X is always an OR group from the initial acetylene dicarboxylic ester. When the acetylenic compound is a diketone and X is an alkyl or aryl moiety, the C=0 group is much more electrophilic and the attack by the Z ion produces an alcoholate (reaction c), a new intermediate which can cyclize on to the P+ to form a phosphorane, or attack the a-C atom to form an ylide as in Scheme 42. Hence, reactions a and c can coexist, and are strongly dependent on the nature of the trapping reagent and of the P compound, but reaction b is blocked, whatever the reagent. This is well illustrated by the reaction of the 2-methoxytetramethylphospholane 147 on diben-zoylacetylene in the presence of methanol as trapping reagent. The proportions of the vinylphosphorane 157 and spirophosphorane 158 formed (Figure 24) are 13% and 84%, respectively.

G.H.N. Towers and D. Champagne, in Chemistry and Biology of Naturally-Occurring Acetylenes and Related Compounds... 

Flores HE, Pickard JJ, Hoy MW (1988) In Lam J, Breteler H, Arnason T (eds) Chemistry and biology of naturally occurring acetylenes and related compounds. Elsevier, Amsterdam, p 233... 

J. Lam, H. Breteler, T. Amason, and L. Hansen, eds., Chemistry and Biology of Naturally-Occurring Acetylenes and Related Compounds (NOARC). Proceedings of a Conference on the Chemistry and Biology of Naturally-Occurring Acetylenes and Related Compounds (NOARC). Elsevier, Amsterdam, 1988. 

The special potential for constructing double bonds stereoselectively, often necessary in natural material syntheses, makes the Wittig reaction a valuable alternative compared to partial hydrogenation of acetylenes. It is used in the synthesis of carotenoids, fragrance and aroma compounds, terpenes, steroides, hormones, prostaglandins, pheromones, fatty acid derivatives, plant substances, and a variety of other olefinic naturally occurring compounds. Because of the considerable volume of this topic we would like to consider only selected paths of the synthesis of natural compounds in the following sections and to restrict it to reactions of phosphoranes (ylides) only. 

It is known that acetylenic bond possesses endothermic cliaracteristics (Vol. Ill, p. 227) and it is interesting to point out that a number of acetylenic compounds were found in nature as early as 1889 [5 and 1892 [6). Currently important are the works of E. R. H. Jones 7 and Bohlmann 8] who isolated and established the structure of numerous naturally occurring polyacetylenes and confirmed their structure by synthesis. Most of the polyacetylenes possess explosive properties. 

Polyacetylenes26 27 exhibit a number of fine-structure bands. Diacetylenes show medium intensity bands (e 100-350) in the 210-250 mp region. Tri- and tetra- and higher acetylenes, however, exhibit very high intensity bands (e > 100,000) at lower wavelengths (200-280 mp) in addition to the medium intensity bands (240-390 mp). Absorption spectra of diphenyl-poiyacetylenes have been reported27 (see references 37 and 38 for naturally occurring acetylenic compounds). 

Gommers, F.J. Bakker, J. In Chemistry and Biology of Naturally-Occurring Acetylenes and Related Compounds Bioactive Molecules-, Lam, J. Breteler, H. Arnason, T Hansen, L., Eds. Elsevier New York, Vol. 7, pp. 61. 

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