Iridomyrmecin synthesis

The synthesis of iridomyrmecin 247) took advantage of the high transannular reactivity which frequently operates in eight-membered rings (vide supm). To this end, 1,5-dimethyl-1,5-cyclooctadiene 243) was monohydroborated, treated with... 

Lee, E., Yoon, C. H. Stereoseiective Favorskii rearrangement of carvone chiorohydrin expedient synthesis of (+)-dihydronepetaiactone and (+)-iridomyrmecin. J. Chem. See., Chem. Commun. 1994, 479-481. 

Transannulation of the mesylate (33), derived from 4,8-dimethylcycloocta-4-en-l-ol, using sodium carbonate in aqueous dioxane has provided the bicyclo[3.3.0]octanol (34), a central precursor to the monoterpene iridomyrmecin (35 equation 13). In studies of the biomimetic synthesis of the natural tri-quinanes capnellene (37 equation 14) and pentalenene (40 equation IS) Pattenden et al. have shown that both molecules can be produced from appropriate cycloocta-l,S-diene precursors, i.e. (36) and (39) [or indeed their corresponding positional isomers (38) and (41), respectively] by treatment with boron trifluoride. Mehta et al. have described an alternative transannulation approach to the triquinane unit found in pentalenene, i.e. (42) - (43 equation 16), and also to the ring system (44 equation 17) found... 

Eight- to sixteen-step syntheses of isoiridomyrmecin and verbenalol,763 iridomyr-mecin764 allodolicholactone (first synthesis), iridomyrmecin and its iso-epimer785 and sarracenin766 have been reported. 

Barton-type deoxygenation of 100, with the same procedure previously described in scheme 20, gave the acetate 101 which is a known intermediate in the synthesis of iridomyrmecin 102. 

Tsunoda et al. [43] have used this asymmetric amide enolate Claisen rearrangement in the total synthesis of (-)-iridomyrmecin 22 (Scheme 5.1.30). Rearrangement of the Z-enolate of the amide 23 via a chair like transition state generated, with a very high diastereoselectivity, the asymmetric centers a and P to the carbonyl group of the natural product. 

Clark et al. (1959) proposed citronellal (V) as a precursor, and were able to synthesize isoiridomyrmecin (II) from this acyclic monoterpenoid as shown below some iridomyrmecin (I) was undoubtedly formed as well, although it was not isolated. In the laboratory synthesis, the aldehyde grouping was protected during the allylic oxidation this would be unnecessary in an enzymatic oxidation. The second step is an intramolecular Michael addition, yielding iridodial (III), the immediate precursor to iridomyrmecins (I and II) in all three schemes. The final step is an intramolecular Cannizzaro reaction. 

Nangia A, Prasuma G. Studies on Homer-Wadsworth-Emmons reaction in base sensitive ketones synthesis of (—)-mitsugashiwalactone and formal synthesis of (- -)-iridomyrmecin, (—)-isoiridomytmecin and (-t-)-teucriumlac-tone. Tetrahedron 1996 52 3435-3450. 

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