Selective Entry to the Dimeric or Oligomeric Pyridinium Sponge Macrocycles via Aminopentadienal Derivatives. Possible Biogenetic Relevance with Manzamine Alkaloids

Abstract

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Chemical synthesis and biological activities of 3-alkyl pyridinium polymeric analogues of marine toxins

“…Previous studies [8,12,15] managed to synthesise only oligo-alkylpyridinium salts, but biological screening of some of them indicated that the pore-forming capability was abolished [19]. This highlighted the importance of high degree of polymerisation for this kind of biological activity.…”

“…Otherwise, refluxing a monomer bearing a terminal chlorine and a linking ether bridge in the alkyl chain, in acetonitrile in the presence of KI for a sustained period, resulted in the production of a mixture of cyclic and linear oligomers with a maximum of 15 monomer units [12]. A rather more sophisticated approach is the formation and subsequent reaction of an N-(2,4-dinitrobenzene) pyridinium salt (Zincke salt) to yield poly-alkylpyridinium salts with up to eight monomer units [15]. The degree of polymerisation can be increased stepwise by the controlled and iterative process of oligomerisation, providing general and practical access to a wide range of linear poly-cationic compounds.…”

Total Synthesis of (±)‐Haliclonacyclamine C

“…10 They believe that intermediates that are more flexible than bis-dihydropyridine macrocycle (1.9) are the biogenetic precursors to manzamine and related alkaloids. Their hypothesis suggests 5-amino-2,4-pentadienal derivatives lead to the production of pyridinium salts (c.f.…”

“…23 followed by reduction and cyclization of the imine functionality to produce enamine 1.24 (Scheme 5). 10 Scheme 5. Marazano's Modification of Baldwin's Approach.…”

“…6 They constructed the unsaturated 13-membered ring using a ring closing metathesis reaction. [9][10][11] They were also able to install the 8-membered ring by a lactamization and introduced the β-carboline unit using the Pictet-Spengler reaction similar to the Winkler and Martin approaches. 7,8 The Pandit synthesis began with L-Serine (2.29), which was transformed to iodide Nakagawa's Approach to Manzamine A (1.3)…”