Alkaloids Martinella

Two pyrroloquinoline alkaloids, martinelline (49) and martinellic acid (50), have been isolated from an organic extract of root of Martinella iquitosensis A. Sampaio (Bigno-niaceae) by Witherup et al. (part of Merck s research group) as bradykinin receptor antagonists (Figure 10.11) [85]. The optical rotations of natural 49 and 50 were reported as [a]o +9.4 and -8.5, respectively, however the synthetic ( ) 50 showed a considerably larger value with the same sense ([a]o-122.7 [86,87] -164.3 [88]). A compound with the... 

Cycloaddition reactions also provide a very straightforward means for the preparation of the quinoline scaffold. Hexahydropyrrolo[3,2-c]quinolines, the core structure of the Martinella alkaloids, were prepared through an intramolecular 3 + 2] azomethine ylide-alkene cycloaddition. Condensation of an aldehyde such as 51 and W-alkyl amino acids followed by decarboxylation and cycloaddition afforded quinoline derivatives such as 52 <01T4095>. The... 

An enantioselective formal synthesis of martinelline using a similar method was developed by Yoshitomi et al. (Scheme 3.6) [24]. Isolated from the roots of Martinella iquitosensis, martinelline 44 and martinellic acid 43 are effective nonpeptidic bradykinin receptor agonists [25]. Furthermore, the structure of these alkaloids possesses an unusually fused pyrrolidinotetrahydroquinoline core, which attracted more attention. Yoshitomi et al. developed a similar, yet more powerful strategy to construct the quinoline core 41 from simple precursors of unsaturated aldehyde 39 with o-aminobenzaldehyde derivative 38. The product desired, 41, was obtained in quantitative yield and 99% ee. 

Martinelline 136 and martinellic acid 137 are classified as pyrroloquinoline alkaloids. They were isolated from the roots of the tropical plant, Martinella iquitosensis, and show bradykinin receptor antagonistic activity. Hamada and co-workers reported on a synthesis of the chiral marti-nellin core structures 134 and 135 via organocatalytic cascade reaction. Anthranilaldehyde 130 and enal 131 underwent Michael-aldol reaction in the presence of (S)-... 

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