Biomimetic heterocyclization

Several current efforts are focusing on the portability of enzymatic heterocyclization. For example, novel chiral heterocyclic carboxylic acids were produced by using hybrid enzymes [62] (Figure 13.21). Stimulated by biosynthesis pathways, biomimetic heterocyclization methods have also been developed with high efficiency [63]. 

The chemistry of nucleic acid analogs has received much attention in recent years, and a series of nucleic acid models has been designed and widely prepared, in order to estimate and utilize their functionalities in relation to the specific basepairing properties ( J., i, ). These monomers and polymers, particularly those containing purines, pyrimidines, nucleosides, and nucleotides, are not only of interest to the field of heterocyclic organic chemistry, but also to that of biomimetic macro-molecular chemistry as synthetic analogs of the nucleic acids. 

Scheme 7.4 Biomimetic synthesis of heterocyclic carboxylic esters.

Escobar, C. A., Kluge, M. and Sicker, D. 1997. Biomimetic synthesis of 4-acetylbenzoxazolin-2(3H)-one isolated from Zea mays. J. Heterocycl. Chem. 34, 1407-1414... 

The reversible FeTe1 FeTe11 couple of an N-heterocyclic carbene dinuclear FeTe1 complex, (p-pdt) [FeI(CO)2(PMe3)][FeI(CO)2(IMes)] (IMes= l,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), complex D, has led to the isolation of the mixed-valent cationic complex D as a biomimetic of the 2Fe2S subsite of the oxidized H cluster in... 

Lounasmaa M, Hanhinen P. Biomimetic formation and interconversion in the heteroyohimbine series. Heterocycles 1998 48 1483-1492. 

Biomimetic synthesis of natural nonfused polycyclic ethers by metal oxide-induced iyn-oxidative polycyclizations of hydropolyenes 98PAC355. Chemical synthesis of cytochrome P-450-dependent metabolites (epoxyeico-satriene acids and other metabolites possessing heterocyclic fragments) 98MI9. 

Toth F, Kalaus G et al (2008) Synthesis of vinca alkaloids and related compounds. Part 109. An intramolecular [4+2] cycloaddition mediated biomimetic synthesis of (+-)-iboxyphyl-line. Heterocycles 75 65-76... 

A biomimetic route for the synthesis of dihydrobenzo[b]furan heterocycles was investigated via a reagent-based electrochemical transformation of 2-(2 -hydroxyethyl)-quinine precursors. It was believed that a putative oxonium ion was generated by treatment of the quinone with PPTS, followed by reduction with dihydroquinone (DHQ) to generate a radical species which underwent either further reduction by DHQ to give the product or a direct dimerization <01JOC4965>. 

The lower rim conjugates of calix[4]arene with these heterocycles are relatively scarce and mostly the larger cavity calix[6]arene scaffold has been used in designing the imidazole-based lower rim hybrids as biomimetic receptors of metalloenzymes. 

Methane hydroxylation A biomimetic approach (heterocycles as ligands... 

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