Macrocyclic tetraether

The method described here gives higher yields of the macrocyclic tetraethers and allows the product from furan and cyclohexanone to be formed directly in 5-10% yield, whereas this product was previously obtained only by an indirect route. The added lithium perchlorate undoubtedly accelerates the reaction, since after short reaction times the product was isolated in 20% yield when the salt was present and in only 5% yield when the salt was absent. The lithium cation is presumably acting as a template which coordinates with the oxygen atoms of... 

In 1972, Vogtle and Zuber condensed 1,2-dibromomethylbenzene (xylylene dibromide) with another xylylene unit, 1,2-dihydroxymethylbenzene. The result was formation of the macrocyclic tetraether (40% yield, mp 194°) shown in Eq. (3.19). The... 

Ether linkages in open-chain bolaamphiphiles were obtained in a 20% isolated yield from a,o)-dibromoeicosane with an alcohol in THF containing sodium hydride (Scheme 2.8). The synthesis of macrocyclic tetraethers was unsuccessful. Attempts to reduce macrocyclic lactones with four ester groups via a variety of methods failed. The production of macrocyclic thioacetals from benzaldehyde derivatives and a,to-dithiols was unproblematic and produced quantitative yields (Scheme 2.8). The cyclization of 2,2-thiodiethanol with a,(o-diols in the melt and in the presence of /7-toluenesulfonic acid is an intermediate case. Apolar macrocycles were obtained in 50% yield. 5-(2-hydroxyethyl)thiiranium ions are presumably formed as reactive intermediates during the ether formation steps. The sulphur atom was oxidized to the... 

Eguchi, T., Ibaragi, K., Kakinuma, K. Total Synthesis of Archaeal 72-Membered Macrocyclic Tetraether Lipids. J. Org. Chem. 1998, 63, 2689-2698. 

Fuhrhop, J.-H., Liman, U., Koesling, V. (1988). A macrocyclic tetraether bolaamphiphile and an oligoamino a, -dicarboxylate combine to form monolayered, porous vesicle membranes, which are reversibly sealed by EDTA and other bulky anions, J. Am. Chem. Soc., 110 6840. 

Originally assigned a branched chain nonitol struct. Correct struct established by synthesis in 1999. Degradation prod, of a complex of macrocyclic tetraether lipids isol. from membranes of thermo-acidophilic archaebacteria of the Cal-dariella group and Methanospirillum species, e.g. Sulfolobus solfataricus, Also found in Methanobacteria spp. 

Syntheses of Archaebacteria 36- and 72-member macrocyclic membrane lipids (di- and tetraethers) 99YGK785. 

It should be mentioned that conditions have been found recently to obtain C4-symmetrical tetraethers 115 directly from resorcinol monoethers by condensation with aldehydes. The regular incorporation in the macrocyclic skeleton was confirmed for one example by X-ray analysis.224 However, in contrast to Heaney s enantioselective synthesis, the racemic mixture of the two enantiomers is formed in this case. 

Lipids of the thermophilic deep-sea methanogen, Methanococcus jannaschii [67] are based largely on the macrocyclic diether (cyc-archaeol, 1C) and consist of mono- and di-glucosyl-cyc-archaeol (20A, 23A, respectively. Fig. 6), P-ethanolamine-glucosyl-cyc-archaeol (20B) and cyc-archaeol-PE (15A) a small amount of archaeol-PE (15) is also present. Mco. Jannaschii is also capable of forming caldarchaeol-derived polar lipids [68], and the proportions of diether, macrocyclic diether and tetraether lipids can vary as a function of growth temperature (see section 5.2). 

Carbenes, generated by photolysis of di- and tetrachloro-o-quinone diazides, react with oxetane in a 1 3 ratio to afford 15-membered crown ethers. Benzocrown ether 675 was obtained in 16% yield (91CB1865). Derivatives of macrocyclic crown ethers with four or five oxygen atoms in a ring were synthesized by Cu(acac)2-catalyzed cyclization of a,polyethylene glycols. 20-26-Membered crown-4(5) ethers 676 were prepared from the above-mentioned diazo ketones with tri- or tetra-ethylene glycols in 7-26% yields. Treatment of l,8-bis(diazoacetyl)octane with dodecane-l,12-diol under the same conditions results in a mixture of 52-membered tetraether 646 (40%) and compound 645 (81CC616). 

The most interesting new polyterpenoids are a series of C40 diols that form part of macrocyclic diglycerol tetraethers which constitute the major membrane lipids of the extremely thermo- and acido-philic bacterium Caldariella. These compounds, (196)—(200), which may be acyclic or may have from one to four isolated cyclopentane rings are formally dimers of C20 isoprenoid structures linked head-to-head rather than the conventional tail-to-tail linkage in, for example, carotenoids.The isoprenoid nature of these compounds has been shown by labelling. 

Patwardhan AP, Thompson DH (2000) Novel flexible and rigid tetraether cyclic and macrocyclic bisphosphocholines synthesis and monolayer properties. Langmuir 16 10340-10350... 

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