Naturally Occurring Thiophens

Naturally Occurring Thiophens. - A review on the formation of heterocyclic compounds, including thiophen derivatives, by enzymic and non-enzymic browning in relation to food flavour has been published.Some thiophens have been found as trace constituents in the essential oil from Thymus capitatus From steam-distilled hop oils, 3-(4-methylpent-3-enyl)thiophen 

Naturally Occurring Thiophens.—Re-investigation of the polar fractions of the aerial parts of Centaurea ruthenica gave, amongst twenty new compounds, 5-hydroxymethyl-2-(3-hydroxypropynyl)thiophen. ° The investigation of two further Helichrysum species led to the isolation of three new unusual thiophen derivatives (137)—(139). New acetylenic thiophen derivatives such as (140) have been isolated from Cullumia setosa.  

Cugnon de Sevricourt, H. El Khashef, and M. Robba, C. R. Hebd. Seances Acad. Sci., 

Naturally Occurring Thiophens.—Bohlmann and co-workers are continuing their extensive investigation of naturally occurring thiophens. From the Indian Compositae Blumea lacera, the acetylenic derivative (261) was 

Naturally occurring Thiophens.—New acetylenic thiophen derivatives are still found in Nature, especially by Bohlmann and his group. From Santolina rosmarinifolia L., the compound (215) was isolated. From the South African family Arctotideae, genus Berkheya, twelve new thiophen-containing derivatives were isolated. One of these was believed to have structure (216), but by elegant synthesis of both (216) and an alternative structure (217), the latter was proved to be correct. Biosynthetic pathways 

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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-... 

PHOTOCHEMICAL AND PHOTOBIOCHEMICAL PROPERTIES OF NATURALLY OCCURRING THIOPHENES AND RELATED STRUCTURES... 

Acetylenic thiophene 2.9, found in some species of higher plants, is one of the few naturally-occurring thiophenes. However, the thiophene ring is used in several important pharmaceutical products, such as the penicillin antibiotic 2.10. 

Tagetes is a very rich source of naturally occurring thiophene derivatives. Various bithiophenes, for example, 12-14 or terthienyl 15, have been identified from Tagetes patula L. Asteraeeae) by GLC-MS analysis <2002ZNC63>. 

Much use has been made of conjugated diynes, which are also at the oxidation level of 1,4-dicarbonyl-compounds, which react smoothly with hydrosulhde or sulhde, under mild conditions, to give 3,4-unsubstituted thiophenes. Unsymmetrical 2,5-disubstituted thiophenes can be produced in this way too. ° Since nearly all naturally occurring thiophenes are found in plant genera, and co-occur with polyynes, this laboratory ring synthesis may be mechanistically related to their biosynthesis. 

Naturally Occurring Thiophens. - From Epaltes species the... 

Ch. 1 Preparation of Thiophenes by Ring Closure Reactions and from Other Ring Systems Ch. 2 Theoretical Calculations on Thiophenes Ch. 3 Naturally Occurring Thiophenes... 

Aldol-type condensations between but-2-enolides and carbonyl compounds constitute probably the most flexible routes to 4-ylidene-butenolides and 4-ylidenetetronic acids. One of the first applications of this general approach was in the preparation of (130) from but-2-enolide (129 a) employing aqueous sodium hydrogen carbonate as base 114). Bohlmann and Zdero 34) later described a synthesis of the naturally occurring thiophene (131) involving condensation between butenolide (129 b) and 5-methylthiophene-2-aldehyde in the presence of piperidine acetate in glacial acetic acid at 80°. 

Naturally-Occurring Thiophenes. Bithienyls from Tagetes minuta L. J. 

Naturally Occurring Thiophenes. IV. Synthesis of some 2,2 -Bithienyl... 

Champagne, D.E., J.T. Arnason, B.J.R. Philogene, G. Campbell, and D.G. Mclachlan Photosensitization and Feeding Deterrence of Euxoa messoria (Lepi-doptera Noctuiidae) by a-Terthienyl, a Naturally Occurring Thiophene from the Asteraceae. Experientia 40, 577 (1984). 

Dicosmo, F., G.H.N. Towers, and J. Lam Photoinduced Fungicidal Activity Elicited by Naturally Occurring Thiophene Derivatives. Pestic. Sci. 13, 589 (1982). 

Hudson, J.B., E.A. Graham, G. Chan, A.J. Finlayson, and G.H.N. Towers Comparison of the Antiviral Effects of Naturally Occurring Thiophenes and Polyacetylenes. Planta Medica 6, 453 (1986). 

Singh, P. Naturally-occurring Thiophene Derivatives from Eclipta Species. Bioact. Mol. (Chem. Biol. Nat.-Occurring Acetylenes Relat. Compd.) 7, 179 (1988). 

Naturally Occurring Thiophens.—The isolation of a terpenoid benzo[ ]-thiophen-4,7-quinone (200) from an acidophilic bacterium has been reported. New naturally occurring acetylenic thiophen derivatives have been isolated from Berkheya and Cullumia species and from Chrysanthemum macrotum. Several naturally occurring acetylenic thiophens have been synthesized. ... 

The reaction between iodothiophens and copper acetylides has been of great use for the preparation of naturally occurring thiophens. " " Reaction of 2,5-dimethyl-3,4-iodothiophen with boron tri-iodide opens the route to... 

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