Butenolide from butanolides

Furfural (18) was oxidized to give the butenolide 19, which on Michael condensation with diethyl ethylmalonate afforded lactone 20. Hydrolysis of 20 yielded the dilactone 21. This was treated with ethanol in the presence of sulfuric acid. The isomer mixture obtained was separated by preparative thin-layer chromatography, yielding 4-ethoxy-3-ethoxycarbonylmethyl-2-ethyl-4-butanolide (22). Elimination of ethanol, with the aid of p-amino-benzenesulfonic acid, gave 2-(3//)-furanone 23 the 2-(5//)-furanone isomer 24 was obtained with the aid of orthophosphoric acid. Both isomeric esters gave the acid 25 after hydrolysis, which on catalytic hydrogenation afforded m-3-carboxymethyl-2-ethyl-4-butanolide 26, identical to homopilopic acid. This synthesis of homopilopic acid differs from earlier syntheses because the less stable cw-2,3-disubstituted butanolide (26) is formed in the last step. 

Bourguignon, J. J. and Wermuth, C. Cj., Lactone chemistry synthesis of p-substituted, f functionali/.ed butanolides and butenolides and succinaldehydic acids from glyoxylic acid, J. Orfi. Chen, 46, 4889. 1981. 

Paleta, O. Palecek, J. Dolensky, B. Fluorinated butanolides and butenolides. Part 8. 2-(Trifluoromethyl)butan-4-olides by synthesis from methyl 3,3,3-trifluoropyruvate as building block. J. Fluorine Chem. 2001, 111, 175-184. 

Trunk wood of Mezilaurus synandra one of the species of Mezilaurus belonging to the same subtribe as Clinostemon, was shown to contain a similar y-lactone, (2/ ,3, 4S)-2-dodec-cu-enyl-3-hydroxy-4-methylbutanolide (41) (mp 72-76°C, [a]o -7.5 ) (115). The butenolide (42) from the same source is considered to be an artificial dehydration product of the 3-hydroxy-lactone (41). All of the above aliphatic y-lactones were isolated from Lauraceae 2-hy-droxy-4-(heptadec-8 -enyl)butanolide (43) obtained as an oil from the bark of Garcinia mannii (Guttiferae) is the only compound of this type found in other families (53). 

Shimoda K, Kubota N, Hirata T, Kondo Y, Hamada H. Stereoselective reduction of 2-butenolides to chiral butanolides by reductases from cultured cells of Glycine max. Tetrahedron Lett. 2007 48 1345-1347. 

Most Other lipidic derivatives are ylactones (butanolides and butenolides), often derived from C20 fatty adds (oxy-lipins) and found especially in Alcyonacea (Litophyton) and Gorgonacea (see below), to which can be added some examples already mentioned from Stolonifera (such as clavulolactone from Clavularia viridis) (see Figures 20.1 and 20.2). 

Figure 20.4 Examples of butanolides and butenolides isolated from Gorgonacea.

Among Gorgonacea, the most original lipidic derivatives may be the butanolides and butenolides isolated from Gorgonidae of the genera Euplexaura, Plexaura and... 

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