Pinnatins A-E: Marine diterpenes of the rare gersolane class derived from a photochemically induced rearrangement of a conjugated 2,5-bridged furanocembrane precursor

Journal of Organic Chemistry

Volumn 63, Issue 13, 1998, Pages 4425-4432

  Rodríguez, Abimael D ^b   Shi, Jian Gong ^b   Huang, Songping D ^b  

^a UNIVERSITY OF PUERTO RICO   (Puerto Rico)

^b NONE

Author keywords

[No Author keywords available]

Indexed keywords

DITERPENE; PINNATIN A; PINNATIN B; PINNATIN C; PINNATIN D; PINNATIN E; UNCLASSIFIED DRUG;

ANTINEOPLASTIC ACTIVITY; ARTICLE; BIOGENESIS; CANCER CELL CULTURE; DRUG SYNTHESIS; NONHUMAN; NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY; PHOTOCHEMISTRY; X RAY CRYSTALLOGRAPHY;

EID: 0032569077     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo980256b     Document Type: Article

References (26)

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4. For previous studies related to P. bipinnata, see: (a) Fenical, W. J. Nat. Prod. 1987, 50, 1001-1008. (b) Wright, A. E.; Burres, N. S.; Schulte, G. K. Tetrahedron Lett. 1989, 30, 3491-3494. (c) Culver, P.; Burch, M.; Potenza, C.; Wasserman, L.; Fenical, W.; Taylor, P. Mol. Pharmacol. 1985, 28, 436-444. (d) Abramson, S. N.; Trischman, J. A.; Tapiolas, D. M.; Harold, E. E.; Fenical, W.; Taylor, P. J. Med. Chem. 1991, 34, 1798-1804.
5. For previous studies related to P. bipinnata, see: (a) Fenical, W. J. Nat. Prod. 1987, 50, 1001-1008. (b) Wright, A. E.; Burres, N. S.; Schulte, G. K. Tetrahedron Lett. 1989, 30, 3491-3494. (c) Culver, P.; Burch, M.; Potenza, C.; Wasserman, L.; Fenical, W.; Taylor, P. Mol. Pharmacol. 1985, 28, 436-444. (d) Abramson, S. N.; Trischman, J. A.; Tapiolas, D. M.; Harold, E. E.; Fenical, W.; Taylor, P. J. Med. Chem. 1991, 34, 1798-1804.
6. For previous studies related to P. bipinnata, see: (a) Fenical, W. J. Nat. Prod. 1987, 50, 1001-1008. (b) Wright, A. E.; Burres, N. S.; Schulte, G. K. Tetrahedron Lett. 1989, 30, 3491-3494. (c) Culver, P.; Burch, M.; Potenza, C.; Wasserman, L.; Fenical, W.; Taylor, P. Mol. Pharmacol. 1985, 28, 436-444. (d) Abramson, S. N.; Trischman, J. A.; Tapiolas, D. M.; Harold, E. E.; Fenical, W.; Taylor, P. J. Med. Chem. 1991, 34, 1798-1804.
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8. 1H NMR data and the m/z value for parent ion of gersolide were reported.
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13. 1H NMR spectrum of the mixture. Subsequent analysis by HPLC was in close agreement.
14. Additional peaks were actually observed during HPLC analysis of the mixture. However, most of these spurious peaks turned out to be minor byproducts arising from concurrent photooxidation of kallolide A (2); see refs 7-9.
15. We find it striking that irradiation with light in 1 leads to a [1,2]-allyl shift product displaying concurrent epimerization of the C-2 stereogenic center. Such a rather unpredictable result was not detected at the end of the [1,3]-allyl shift process. Though photochemical epimerizations usually imply that a radical intermediate might be involved in the course of the reaction, such an explanation would be inconsistent with the apparent high diastereoselectivity of the process. The difference in reactivity in 1 at C-2 during these sigmatropic rearrangements is unclear.
16. a] cycloaddition reaction, see: Woodward, R. B.; Hoffmann, R. The Conservation of Orbital Symmetry; Verlag Chemie, Weinheim, and Academic Press: New York, 1970.
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18. For fundamental studies of photochemical [1,2]-allylic rearrangements; see (a) McCullough, J. J.; Manning, C. J. Org. Chem. 1978, 43, 2839-2842. (b) Akhtar, I. A.; McCullough, J. J.; Vaitekunas, S.; Faggiani, R.; Lock, C. J. L. Can. J. Chem. 1982, 60, 1657-1663.
19. Addition of the a bond is antarafacial if one terminus suffers inversion while the other suffers retention. In bipinnatin J (1), H-7 and Me-19 are cis. On the other hand, in pinnatin A (3) these groups end up being trans after the rearrangement. This is consistent with a mechanism in which the C9-C10 σ bond in 1 migrates antarafacially to C-7 and C-8, respectively, with inversion of configuration (undetectable) at one of the reaction termini and retention at the other (observed) to produce pinnatin A.
20. Although antarafacial cycloaddition processes are impossible for transformations which occur within small or medium-sized rings, when the migrating group of atoms possesses an accessible σ orbital and is not so substituted as to create an impossible steric situation in the transition state, alternative processes using that σ orbital must be considered, and clearly, such changes must proceed with inversion at the migrating center. See: Woodward, R. B.; Hoffmann, R. Angew. Chem., Int. Ed. Engl. 1969, 8, 781-853.
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