Oroidin alkaloids

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. 

Jimenez, C., Crews, P., (1994). Mauritamide A and aceompanying oroidin alkaloids corathQspoagQ Agelas mauritiana. Tetrahedron Lett. 35, 1375-1378. 

Orius insidiosus, 4098 Orixa, 722 Ornithine, 365,417 L-Omithine, 344 Ornithine decarboxylase, 182 Ornithonyssus sylviarum, 4072 Orobanchaceae, 3585 Orobanche, 3585 Orobanche minor, 3591 Orobanchol, 3585 Orobanchol series, 3589 Orobol, 1667 Oroidin alkaloids, 265 Orotic acid, 1664 Orsaponin, 3235 OrtAo-chloranil, 1063 Orthologous/homologous, 698 Orthostatic hypotension, 697, 1373 Orawacin, 3027... 

Probably related to keramidine (see above), laughine is another example of an oroidin alkaloid in which the aminoimidazole part is replaced by a guanidine. It was isolated with dominicin from the species Eurypon laughlini (see above) (Williams et al, 2005b). 

Wang, S Dilley, AS., PouHermec, K.G., and Romo, D. (2006) Planned and unplanned halogenation in route to selected oroidin alkaloids. Tetrahedron, 62, 7155-7161. 

Mourabit AA, Potier P (2001) Sponge s Molecular Diversity Through the Ambivalent Reactivity of 2-Aminoimidazole A Universal Chemical Pathway to the Oroidin-Based Pyrrole-Imidazole Alkaloids and Their Palau amine Congeners. Eur J Org Chem 237... 

Pyrrole-imidazole Alkaloids Oroidin -Related Alkaloids... 

This class of bromopyrrole alkaloids includes all those molecules whose cyclized skeleton can be formally derived through the formation of one (or more) C-C or C-N bonds within the oroidin framework. Consequently, we have found it very useful to classify these molecules according to the oroidin atoms involved in the formal cyclization. More than 40 molecules have been thus classified into six different groups. 

The parent compound of this class is cyclooroidin (38), isolated from the Mediterranean sponge Agelas oroides [40]. Two syntheses of this alkaloid have been proposed [66,67], and one of them, obtaining rac-cyclooroidin by intramolecular cyclization of oroidin formate at 95 °C in protic solvents, could have biomimetic significance [67]. 

Phakellins (41, 42), tetracyclic derivatives in which both the pyrrole and the amidic nitrogen atoms are involved in the formation of a linkage with carbon atoms of the imidazole ring, represented the first members of the family of oroidin-related cyclic bromopyrrole alkaloids to be isolated. They were found in 1971 by Sharma et al. in the marine sponge Phakelliaflabellata their structure was confirmed by X-ray diffraction analysis of a single crystal of the monoacetyl derivative of 41 [70]. Complete spectral data were provided by the same authors a few years later [71]. 

Different molecular mechanisms have been separately postulated for dibromo-phakellin [74], dibromoagelaspongin [91], agelastatin [92], mauritiamine [88], and palau amine [78]. A1 Mourabit and Potier proposed a universal chemical pathway, starting from the simple precursors 101 and 140 and leading to over 60 pyrrole-imidazole alkaloids [80]. A new biomimetic spontaneous conversion of proline to 2-aminoimidazolinone derivatives using a self-catalyzed intramolecular transamination reaction together with peroxide dismutation as key step has been described [166]. This work has pointed to dispacamide A as the forerunner of oroidin and compounds 101 and 140 as probable hydrolysis products of oroidin and not the precursors. In this... 

There have been very few reports of the combined use of computer-assisted structure elucidation methods that have employed any form of data, whether direct or long-range correlation. Two papers appeared in 1999, the first by Kock, Junker, and Lindel [43]. These authors compared the application of computer-assisted structure elucidation methods to the alkaloid oroidin (3) with and without the inclusion of chemical shift correlation data. The tabulated results obtained for oroidin and reported in the study are quite interesting in terms of the impact of the availability of chemical shift correlation data. 

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