1P9: g) Synthesis of cationic β-vinyl substituted meso-tetraphenylporphyrins

 E. M. P. Silva et al.³⁶ synthesized an easy route to cationic β-vinyl substituted meso-tetraphenylporphyrin derivatives are described. Two novel compounds were tested in vitro for their antiviral photoactivity against herpes simplex virus type 1. One of these compounds exhibited a significant activity, reaching 99% of virus inactivation after 15 min of photoactivation. 2- and 4-alkylpyridines are known to undergo aldol-like condensations with carbonyl compounds upon treatment with strong bases; the use of N-alkylpyridiniums allows the reaction to occur under milder conditions, as a consequence of the electron withdrawing effect exerted on the ring by the presence of the positive charge.³⁷ They evaluated the possibility of using such aldol-like reaction on 2-formyl-5,10,15,20-tetraphenylporphyrin (29) in order to afford the desired monosubstituted cationic derivatives 30 and 31 in a one-step process (Scheme 9).

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36. E. M. P. Silva, F. Giuntini, M. A. F. Faustino, J. P.C. Tome´, M. G. P. M. S. Neves, A. C. Tome´,  A.M. S. Silva, M. G. Santana-Marques,  A. J. Ferrer-Correia,  J. A. S. Cavaleiro, M. F. Caeiro, R. R. Duarte, S. A. P. Tavares, I. N. Pegado, B. d’Almeida, A. P. A. Matos, and M. L. Valdeira, Bioorg. Med. Chem. Lett., 2005, 15, 3333.

37. (a) B. C. Uff, A. R. In Katrizky, and C. W. Rees, Eds. ‘Comprehensive Heterocyclic Chemistry’, Pergamon, Oxford, 1995; Vol. 2, p 229; (b) D. Jerchel, and H. D. Heck, Liebigs Ann. Chem. 1958, 613, 171.

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