Stereoselective preparation of (5E)- and (5Z)-5-benzylidene-3-methyl-3-pyrrolin-2-ones. Application to the synthesis of ampullicine and isoampullicine

Tetrahedron Letters

Volumn 37, Issue 32, 1996, Pages 5809-5812

  Rico, Rosario ^a   Bermejo, Francisco ^a  

^a UNIVERSITY OF SALAMANCA   (Spain)

Author keywords

[No Author keywords available]

Indexed keywords

AMPULLICIN; ISOAMPULLICIN; PYRROLINE DERIVATIVE; SESQUITERPENE; UNCLASSIFIED DRUG;

ARTICLE; CHIRALITY; DRUG SYNTHESIS; REACTION ANALYSIS; STEREOCHEMISTRY;

EID: 0030570851     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/0040-4039(96)01232-4     Document Type: Article

References (16)

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2. 2. Byrne, L. T.; Guevara, B. Q.; Patalinghug, W. C.; Recio, B. V.; Ualat, C. R.; White, A. H. Aust. J. Chem., 1992, 45, 1903-1908.
3. 4 (LDA, THF, -78 °C) reacted with a range of aldehydes, giving mixtures of erythro and threo isomers. Yields ranged from 65% to 85%, with a marked preference for the erythro diastereomer (from 3:1 to >98: 2, increasing with the steric bulk of the aldehyde). Martin, M. J. unpublished results.
4. 4. Martin M. J.; Bermejo F. Tetrahedron Lett., 1995, 42, 7705-7708.
5. 5. Casiraghi, G.; Rassu, G. Synthesis, 1995, 607-626;
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10. 7. Lowry, T. H. and Richardson K. S. "Mechanism and theory in Organic Chemistry" Harper and Row, Publishers, Third Ed. New York. 1987. pp 591-595.
11. 8. Similar allylic bromination has been achieved with but-2-enolides: Steyn, P. S.; Conradie, W. J.; Garbers, C. F.; de Vries, M. J. J. Org. Chem., 1965, 30, 3075-3079; Ingham, C. F.; Massy-Westropp, R. A. Aust. J. Chem., 1974, 27, 1491-1503.
12. 8. Similar allylic bromination has been achieved with but-2-enolides: Steyn, P. S.; Conradie, W. J.; Garbers, C. F.; de Vries, M. J. J. Org. Chem., 1965, 30, 3075-3079; Ingham, C. F.; Massy-Westropp, R. A. Aust. J. Chem., 1974, 27, 1491-1503.
13. 1HNMR analysis). The rationale under this result may reside in the formation of an alkoxyphosphonium intermediate 15 formed through bromide displacement in 11 by the triphenyl phosphine. This species may promote the condensation with benzaldehyde leading to a benzylic alkoxonium derivative 16, which would undergo elimination (triphenyl phosphine oxide) giving rise to a benzylic carbonium ion 17 which will collapse with concomitant N-BOC deprotection to the thermodynamically more stable isomer Z-10, as the major component of the reaction mixture. (See Ref. 10). (formula presented)
14. 10. House, H. O. "Modern synthetic reactions". Benjamin-Cummings Publishing Company. Second edition. Menlo Park California 1972. pp 698.
15. 1HNMR analysis of the crude reaction mixture.
16. 12. Rico, R; Bermejo, F. Tetrahedron Lett., 1995, 36, 7889-7892.