Mono-tetrahydrofuran ring

Jiang Z, Chen Y, Ruo-Yun CH, De-Quan Y. Mono-tetrahydrofuran ring acetogenins from Goniothalamus donnaiensis. Phytochemistry 1997 46 327-331. 

In contrast to the relative chemical stability of mono-epoxides, diol epoxides of fatty acids (10.52), which are formed from di-epoxides by EH, are subject to a different fate. In such metabolites, intramolecular nucleophilic substitution may occur, such that oxirane opening is accompanied by formation of a tetrahydrofuran ring [134], Such reactions of intramolecular nucleophilic substitution are discussed in detail in Sect. 11.9. In the case of diol epoxides of fatty acids, the resulting tetrahydrofuran-diols (10.53) are part of a much larger ensemble of oxygenated metabolites of fatty acids, the potential cytotoxicities of which are being evaluated [135]. 

Annonaceous Acetogenins with Mono-Tetrahydrofuran (THF) Ring... 

Diastereoselective ring opening of mono- and bicyclic anhydrides with sodium (S)-4-isopropyl-2-thioxothiazolidinide is an attractive alternative 10°. Aminolyses are carried out in tetrahydrofuran at low temperatures in a 1 1 molar ratio in the absence or presence of additives such as HMPA, TMEDA or DMSO. High yield and diastereoselectivity are recorded in the case of 4-cyclohexene-1,2-dicarboxylic anhydride. /... 

The directly bonded C—coupling constants have been used to give a measure of aromaticity in mono- and polycyclic hydrocarbon ring systems.Cyclo-octatetraene reacts with methylene dichloride and methyl-lithium to afford a mixture of syn and anti-9-chlorobicyclo[6,l,0]nona-2,4,6-triene (40 and 41) which, on treatment with a 30% lithium dispersion in tetrahydrofuran, gives cyclonona-tetraenide, which is isolated as the tetraethylammonium salt. The chemical shift and the coupling constant (7i3c-ih = 137 c./sec.) observed for the lithio-salt (42) are indicative of the aromatic character of the ring, in accord with the predictions of Hiickel s Aromaticity rule. 

Saturated and mono-unsaturated 5- and 6-membered rings can be metallated in the same way as their acyclic analogues. In the case of tetrahydrofuran however, warming with n-butyllithium produces a lithio-derivative which undergoes a... 

The ring-opening of the antf-9-methoxy compound CXIV) should proceed in a conrotatory fashion to provide the wyno-trans ion (XII), and when (XIV) was treated with an alkali metal in tetrahydrofuran at low temperatures a salt of this mono-trans ion was obtained and characterised by its n.m.r. spectrum [62,64]. 

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