Dimeric pyrrole-imidazole alkaloids

O Malley DP, Li K, Maue M, Zografos AL, Baran PS. Total synthesis of dimeric pyrrole-imidazole alkaloids sceptrin, ageliferin, nagelamide E, oxysceptrin, nakamuric acid, and the axinellamine carbon skeleton. J. Am. Chem. Soc. 2007 129 4762-4775. 

Scheme 9.18 Asymmetric total syntheses of dimeric pyrrole-imidazole alkaloids, (—)-palau amine, (—)-axinellamines, and (—)-massadines...

The first examples of tetrameric pyrrole imidazole alkaloids, stylissadine A (100) and B, were isolated from the Caribbean sponge Stylissa carihica in 2006 [128]. They possess a symmetric dimeric stmcture derived from condensation of two massadine units, and differ in the configuration at the center C-2. Stylissadines represent the largest pyrrole-imidazole alkaloids isolated so far, and, with their 16 stereogenic centers, they are the most complex stmctures known within the oroidin alkaloid family. 

Pyrrole-imidazole alkaloids structures can vary with regard to (a) oxidation, reduction or hydration of the 2-amino -4(5)-vinylimidazole unit, (b) dimerization, and (c) cyclization. The... 

Vhh conplings together with chemical shifts have been calcnlated by Chini et al for kedarcidin chromofore and palau amine in the attempt to establish the correct configuration of these two compoimds prior to their total synthesis. Kedarcidin chromofore is a compoimd that belongs to the enediyne family of antitumor antibiotics, whereas palau amine is an oroidin dimer, belonging to the class of pyrrole-imidazole alkaloid family isolated from the sponge Stylotella aurantiwn. Populations of conformers in three cinchona alkaloid O-ethers at ambient and low temperatnres have been estimated by Bnsygin et al ... 

Among the more complex structures, carteramine A and stylissadines A and B are respectively dimers (C22N10) and tetramers (C44N20) of C11N5 pyrrole-imidazole alkaloids. Isolated from the species Stylissa carteri harvested in Japan, carteramine A is an inhibitor of neutrophil chemotaxis (IC50 5 pM), and may lead to a new generation of anti-... 

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