Macrocycles containing furan rings

Continuous interest in macrocyclic systems containing furan rings spans more than 25 years. Very often the furan ring has been used merely as a structural element, the interest of the work lying elsewhere sometimes the macrocyclic system contains heterocyclic units other than furan rings. We shall confine ourselves to macrocycles containing furan units where the chemistry of the furan is more than passing interest. Readers concerned with a much fuller account can consult the review by Newkome et al.25b... 

Goswami S, Dey S, Jana S (2008) Design and synthesis of a unique ditopic macrocyclic fluorescent receptor containing furan ring as a spacer for the recognition of dicarboxylic acids. Tetrahedron 64 6358-6363... 

Although 50 possesses a ring current, the derivative 53, containing three methoxycarbonyl substituents does not. This is a result of a severe steric interaction between the substituents and the furan rings, which is evidently sufficient to destroy the planarity of the macrocyclic ring i 5>. 

The structure of nonactin was elucidated by Gerlach and coworkers, who found that nonactin was a macrocyclic ester consisting of four alternating units of levorotatory and dextrorotatory nonactic acid, a hydroxy acid containing a cis-tetrahydro-furan ring. In 1975, the structure of nonactin was confirmed by total syntheses by Gerlach and by Schmidt. ... 

Numerous macrocyclic and macropolycyclic ligands featuring subheterocyclic rings such as pyridine, furan or thiophene have been investigated [2.70] among which one may, for instance, cite the cyclic hexapyridine torands (see 19) [2.39] and the cryptands containing pyridine, 2,2 -bipyridine (bipy), 9,10-phenanthroline (phen) etc. units [2.56,2.57,2.71-2.73]. The [Na+ c tris-bipy] cryptate 20 [2.71] and especially lanthanide complexes of the same class have been extensively studied [2.74, 2.75] (see also Sect. 8.2). 

In 2008, Donohoe and coworkers reported the total synthesis of (—)-(Z)-deoxpukalide (1) [30], a complex marine natural product with an intriguing 14-membered carbon macrocyclic skeleton containing a trisubstituted furan moiety (Fig. 1). The key features in the synthesis involve a selective alkene RCM/aromati-zation protocol to prepare the disubstituted furan methyl ester (3) as well as a late stage RCM to furnish the butenolide moiety. Since the five-membered ring formation is more favored, the marked exomethylene functionality was intact under the alkene RCM conditions. 

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