Metaboliten aus marinen Ciliaten mit einem neuartigen C30-Rückgrat

Guella, Graziano; Dini, Fernando; Pietra, Francesco

doi:10.1002/(sici)1521-3757(19990419)111:8<1217::aid-ange1217>3.0.co;2-p

Angewandte Chemie

1999

DOI: 10.1002/(sici)1521-3757(19990419)111:8<1217::aid-ange1217>3.0.co;2-p

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Metaboliten aus marinen Ciliaten mit einem neuartigen C30-Rückgrat

Graziano Guella

Fernando Dini

Francesco Pietra

Abstract: Die biosynthetische Herkunft des neuen Ciliatenmetaboliten Vannusal A 1, der ein neuartiges C30‐Gerüst aufweist, wirft herausfordernde Fragen auf.

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Cited by 20 publications

(5 citation statements)

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“…However, strains from southern Brazil, Tenerife, and northeastern and southeastern Australia produce two sesquiterpenoids, rarisetenolide and its epoxide, while a strain from New Zealand produces epirarisetenolide [17]. Strains that are now recognized within this same morphospecies, collected at the same spot in Brazil or in New Zealand, produce two families of related diterpenoids, in which the isopropylidene group is prenylated [18]. Thus, it is beyond doubt that E. rariseta shows polymorphism, perhaps including strains that had been assigned to new species, like Euplotes focardii Valbonesi and Luporini, 1990.…”

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confidence: 90%

“…Oxepane-type C 15 acetogenins were only known for Laurencia nipponica from Japan [2], until they were discovered as the preferred mode of heterocyclization by L. microcladia Kützing, 1865 from a very restricted tract of coast called Il Rogiolo-no more than a few hundred meters in length-in the Ligurian Sea, south of Livorno (Fig. 2).…”

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confidence: 99%

“…A simple thin-layer chromatography (TLC) kit was devised to quickly recognize this protozoan as E. crassus (Fig. 5) [12]. With such an array of homogeneous specimens, taxonomic keys based on morphological observations could also be refined, and we acquired the skill to distinguish typical specimens of E. crassus from E. vannus.…”

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confidence: 99%

“…In contrast with the former, E. vannus proved polymorphic (Fig. 6); a sample from the Côte d'Azur gave both a reduced form of preuplotin and a cyclized form presumably deriving from it [13]. Sampled in the Celebes Sea, E. vannus remarkably gave instead a bisacetylated C 30 metabolite, vannusal A [14].…”

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confidence: 99%

“…Subsequent preliminary identification of a sesquiterpene isolated from this ciliate that resembles halved vannusal A (Fig. 6) suggests, however, a biogenesis via the coupling of two molecules of sesquiterpenes [15].…”

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confidence: 99%

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Evolution of the secondary metabolite versus evolution of the species

Pietra¹

2002

Pure and Applied Chemistry

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Four stereochemical series of diastereomeric polyhalogenated chamigrane sesquiterpenes-headed by obtusol, isoobtusol, rogiolol, and cartilagineol-suggest the existence of four lineages of red seaweeds in the genus Laurencia. On another front, concerning marine ciliates, euplotane sesquiterpenes characterize worldwide the morphospecies Euplotes crassus, well differentiated from Euplotes raikovi, Euplotes rariseta, and Euplotes vannus, which furnish different-skeleton sesquiterpenoids, and the latter also C 30 -backbone isoprenoids. The latter three morphospecies, however, show polymorphism in the variability of their isoprenoids.Unarguably, the modern construction of phylogenetic trees and evolutionary events concerning species is based on molecules that are found in all organisms, such as rRNA coding fractions and highly conserved proteins for long distances, or polymorphic enzymes for population structure and dynamics. However, the correlation between gene and protein expression is low, and that between proteins and secondary metabolites is even lower, which throws much shadow on "lower" species that compete for space and resources, or defend themselves from predators, largely thanks to secondary metabolites. These often constitute their best taxonomic and phylogenetic markers. In this regard, biologists and natural products chemists live largely in separate, artificial worlds-the evolutionary biologist snubbing the secondary metabolite, and the chemotaxonomy of the natural products chemist providing little trait d'union, as it is typically concerned with gross comparisons of identities or similarities in molecular structures that ignore deep-seated chemical features.An example of gross structural comparison concerns a nominal species of red seaweed, Laurencia microcladia Kützing, 1865, of Atlantic origin although rather common in infralittoral areas of the Mediterranean (Fig. 1). The story begins with a sample of this seaweed from Cap Ferrat, along the Côte d'Azur, giving new polyhalogenated C 15 acetogenins, a class of compounds unique to seaweeds in the genus Laurencia and opisthobranch mollusks that feed on them. In this case, these are of the most com-*Lecture presented at

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confidence: 90%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Evolution of the secondary metabolite versus evolution of the species

Pietra¹

2002

Pure and Applied Chemistry

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A Catalytic Asymmetric Three‐Component 1,4‐Addition/Aldol Reaction: Enantioselective Synthesis of the Spirocyclic System of Vannusal A

Nicolaou¹,

Tang²,

Dagneau³

et al. 2005

Angewandte Chemie

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Total Synthesis of the Originally Assigned Structure of Vannusal B

et al. 2008

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Vannusals A (1 a, Figure 1) and B (1 b) are two marine natural products notable for their unusual molecular architectures. Isolated from the tropical interstitial ciliate Euplotes vannus strains Si121 and BUN3, these intriguing molecules include in their C 30 molecular framework seven rings and thirteen stereogenic centers, three of which are quaternary. Their structures have been assigned on the basis of mass spectrometric and NMR spectroscopic data and chemical transformations. [1,2] Herein we report the total synthesis of structure 1 b that proved that it does not represent the true structure of vannusal B.Our retrosynthetic analysis of the vannusal molecule dissected it as shown in Figure 2, revealing vinyl iodide 2 and aldehyde 3 as the key building blocks required for the projected total synthesis. The devised strategy anticipated their fusion through two carbon-carbon bond-forming reactions, namely lithiation of 2 followed by addition of 3 to join them, and a samarium-induced ring closure of a subsequent intermediate to forge the final ring of the target molecule.Scheme 1 summarizes the construction of vinyl iodide 2 from the commercially available meso diol 4. Thus, dehydration of 4 through the action of POCl 3 (py, 90 8C) furnished conjugated diene 5 (97 % yield), [3] which was regio-and stereoselectively converted into the new meso diol 6 by a hydroboration-oxidation process (CyBH 2 ; H 2 O 2 , NaOH, 51 % yield). The latter compound was then desymmetrized through the enantioselective hydrolytic action of Lipase Amano PS [4] on its bis-acetate (prepared in quantitative yield by reaction of 6 with Ac 2 O in the presence of 4-DMAP), leading to the monoacetate 7 in 100 % yield and 99 % ee (determined by Mosher ester analysis). Silylation of 7 (TBDPSCl, imid, 93 % yield) followed by acetate cleavage (DIBAL-H, 98 % yield) and treatment of the resulting alcohol with Martins sulfurane (Et 3 N, CH 2 Cl 2 , 91 % yield) afforded enantiomerically pure cyclopentene derivative 8. The planned stereoselective epoxidation of 8 was achieved through a two-step procedure that involved first iodohydrin formation (NIS, H 2 O), and then ring closure (K 2 CO 3 , MeOH) to give b-epoxide 9 in 91 % overall yield. This epoxide was then regio-and stereoselectively opened with 2-lithiopropene (generated from the corresponding bromide and tBuLi) in the presence of BF 3 ·Et 2 O to afford hydroxy compound 10 (83 % yield), whose stereochemistry was inverted through application of a Mitsunobu (pNO 2 C 6 H 4 CO 2 H, Ph 3 P, DEAD) [5] /ester cleavage (DIBAL-H) protocol, leading to the desired hydroxy compound 11 in 90 % overall yield. With the proper stereochemistry now installed on 11, a BOM group was placed on the free hydroxy group (BOMCl, iPr 2 NEt) and the TBDPS group was removed (TBAF, 97 % overall yield) to furnish compound 12. The newly generated hydroxy group within 12 was then oxidized [NMO, TPAP (cat.), 96 % yield], and the resulting ketone was converted into its tris-hydrazone 13 (TrisNHNH 2 , 80 % yield). Finally, the targeted...

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Metaboliten aus marinen Ciliaten mit einem neuartigen C30-Rückgrat

Abstract: Die biosynthetische Herkunft des neuen Ciliatenmetaboliten Vannusal A 1, der ein neuartiges C30‐Gerüst aufweist, wirft herausfordernde Fragen auf.

Cited by 20 publications

References 12 publications

Evolution of the secondary metabolite versus evolution of the species

Evolution of the secondary metabolite versus evolution of the species

A Catalytic Asymmetric Three‐Component 1,4‐Addition/Aldol Reaction: Enantioselective Synthesis of the Spirocyclic System of Vannusal A

Total Synthesis of the Originally Assigned Structure of Vannusal B

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