Manzamine structure

The unique structure and extraordinary bioactivity of manzamine alkaloids have attracted great interest from synthetic chemists as one of the most challenging natural product targets for total synthesis. Great efforts have been made to achieve total synthesis of manzamine A and related alkaloids. Methodological studies towards the synthesis of manzamine structural units have also been reported [31-33]. 

Manzamine alkaloids have been the subject of numerous synthetic studies owing to their novel molecular structure coupled with promising biological properties. Most of the synthetic studies on manzamine alkaloids focused on the construction of the ABCDE pentacyclic lower half of the manzamine structure. 

Structures of marine sponge alkaloids manzamines and related compounds 97H(46)765. 

Marine sponges are a source of an array of polycyclic diamine alkaloids of common biogenetic origin. This class of secondary metabolites has been the subject of four previous reviews [4-7]. Therefore, the present review will include literature reports previously not discussed, dealing with the isolation, structure determination, biological activities, and total synthesis of polycycUc diamine alkaloids isolated from marine sponges. This review will not include guanidine alkaloids [8,9] or the manzamine alkaloids [10,11], since these compounds have been recently reviewed elsewhere. Only polycycUc... 

The polycyclic structure of manzamine A 74, an alkaloid with promising antitumor activity, constitutes an ideal testing ground for probing the effciency of RCM. Although no total synthesis of 74 has yet been reported, various approaches to this complex target rely on RCM-based strategies. 

Manzamine alkaloids can be isolated from marine sponges. They often contain /3-carboline. This group has a diverse range of bioactivities. It also has its own way of establishing its structures. An intramolecular Diels-Adler reaction for manzamines has been proposed. The a is bisdihydropyridine (derived probably from amonia), and the (3 is intramolecular cycloaddition in a pentacyclic... 

The manzamines are novel polycyclic p-carbolinealkaloids reported first by Higa and coworkers in 1986,73 from the Okinawan marine sponge Haliclona. Manzamines have been shown to have a diverse and interesting range of bioactivity including cytotoxicity and antimicrobial and insecticidal activities.74 75 Isolation ( 0.85% dry weight) and structure elucidation, aided by 15N-NMR spectroscopy, of the known manzamine A (59), and the... 

Manzamines comprise a new group of /3-carboline alkaloids having polycyclic ring systems, the provenance of which is problematical as there appears to be no obvious biogenetic path. Manzamine A (180) was isolated from an Okinawan sponge (Haliclona sp.) and shown to exhibit antitumor activity. Its structure and absolute configuration were determined by X-ray analysis (150). From an Okinawan sponge (Pellina sp.) keramamines A (180) and B (181) were isolated as antimicrobial substances (151), and keramamine A was found to be identical with manzamine A. 

Further investigation of the Okinawan sponge Haliclona sp. resulted in the isolation of manzamines B-F (182-186), which show cytotoxic activity (152-154). The structures of manzamines B (182) and C (183) were based on X-ray analysis. Manzamine F (186) was found to be identical with keramamine B, the structure of which with a 1,2,3-triazacyclohexane moiety (181) was revised to structure 186 containing a hexahydro-5(2//)-azocinone ring. Total synthesis of manzamine C (183) was achieved by the... 

For the structurally more complex molecule 18, only the Schrock conditions worked. Compound 18 has been synthesized as a synthetic precursor of the marine alkaloid nakado-marin A (19 [14]) from the marine sponge Amphimedon sp. Nakadomarin A (19) belongs to the manzamine alkaloids, which are also targets of biomimetic syntheses [15], For both strategies, there is still some distance to go. 

There are several reviews referring to manzamine alkaloids [7,31-35]. In this chapter, we will review the structure and source of manzamine alkaloids including the large-scale preparation of manzamine alkaloids for preclinical evaluation. We also discuss the detailed synthesis and bioactivities of manzamine alkaloids. 

The motuporamines are considered as manzamine-related alkaloids owing to their structural relationship with manzamine C (57), the simplest alkaloid of this family of compounds. Baldwin and Whitehead have proposed a plausible biogenesis for these 3-alkylpiperidine alkaloids, suggesting that they could be formed from three basic building blocks ammonia, a C3 unit, and a Cio unit [54]. The motuporamines, which contain a spermidine-like side chain instead of the alkylated p-carboline substructure of manzamine C, appear to be biogenetically derived from the same precursors, ammonia, acrolein, and a long-chain dialdehyde involved in the Baldwin-Whitehead pathway (Scheme 9.2). 

Polycyclic amine alkaloids (3-alkylpiperidine alkaloids) containing a complex skeleton with several macrocyclic rings have been isolated from marine sponges. They include manzamines, sarains, haliclamine A and ingenamines. Their structures, synthesis and biochemical aspects have been recently reviewed [35]. Our focus, therefore, is on the biogenetic origin of the bis-pyridinium macrocycle and on the role of precursors in their biosynthesis, as summarized in the retrosynthetic analysis for manzamines demonstrated schematically in Fig.(23). 

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