Polyacetylenes naturally occuring

The ease with which thiophenes are formed in the reaction of acetylenic epoxides " and of polyacetylenes with hydrogen sulfide is of great interest in connection with the biosynthesis of the naturally occurring thiophenes (cf. Section VIH,A) and also of preparative importance. 2-Methyl-l,2-oxido-5-hexene-3-yne (56) in water containing barium hydroxide reacts with HzS at 50°C to give 4-... 

Anchel, M. Some Naturally Occurring Antibiotic Polyacetylenes. Trans. 

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

Both synthetic and naturally occurring polymers have been used as CSPs. Figure 3.2 shows typical CSPs prepared from optically active polymers (1-18) 1-15 are totally synthetic polymers, including vinyl polymers (1-7), polyamides (8-12), polyurethanes (13), polyacetylene (14), and polysaccharide analogue (15). The CSPs 16-18 are based on natural polymers, proteins (16), and polysaccharides (17, 18). 

Bohlmann, R, Burkhardt, T. and Zdero, C. (1973) Naturally Occurring Polyacetylenes. Academic Press, London. 

The chemistry of acyclic, synthetic polyacetylenes will be considered in this chapter. Cyclic and naturally occuring polyacetylenes are covered in separate chapters. Although most of the discussion is directed toward conjugated polyynes, reactions of non-conjugated derivatives are included in which interactions between triple bonds play an important role. Earlier work in the area has been reviewed thoroughly and consequently in this chapter attention is directed mainly toward some of the more recent advances. 

The spectra of conjugated polyenepolyynes are often very complex and difficult to analyse. When the acetylenic part is the major chromophore, e.g. in an enepolyyne, the spectrum resembles that of a pure polyyne, but when the ethylenic portion constitutes the major chromophore, the spectrum is closer to that of a regular polyene -. Much of the information about polyenepolyynes can be found in works dealing with naturally occurring polyacetylenes. ... 

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. 

Some naturally occurring polyacetylenes of DahUa species. 

Flores, H. E., J. J. Pickard, and M. W. Hoy, Production of polyacetylenes and thiophenes in heterotrophic and photosynthetic root cultures of Asteraceae, in Naturally Occurring Acetylenes and Related Compounds (J. Lam, H. Breteler, T. Amason, and L. Hansen, eds.), 233-254, Elsevier, Amsterdam, 1988. 

The phototoxic effects of naturally occurring polyacetylenes and a-terthienyl have been further studied by Wat, Towers, Lam, and co-workers. Hemolysis, potassium ion leakage, and acetylcholinesterase inhibition were produced by these compounds in human erythrocytes, the effect being enhanced by long wave-... 

These compounds have been investigated thoroughly by Bohlmann s and Schulte s teams. Up to now, about 150 alkynes have been isolated [217, 333]. Schulte et al. [230] recommend sihca gel G layers for separating naturally occurring polyacetylene compounds which are... 

A group of new amphiphilic macromolecules comprised of hydrophobic polyacetylene backbone and hydrophilic pendant groups of naturally occurring species such as amino acids, saccharides, and nucleosides are synthesized. The polymers exhibit solvatochromism. The macromolecular chains show helical confommtions that depend on the molecular structures of the pendants, solvent, temperature, pH, and additives. 

It is clear now that solvent environment can affect the chain conformations of tile polyacetylenes carrying the pendants of naturally occurring building blocks. This suggests the possibility of tuning the chain heiicity by external stimuli and we thus pursued the helical manipulation. 

Table 1. Naturally Occurring Ylidenebutenolides Co-Occurring With Polyacetylenes...

Naturally Occurring Poly olefinic and Polyacetylenic Compounds... 

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