%0 Journal Article
%T Study Toward the Total Synthesis of Pyrenophorin Estudos visando a s¨ªntese total da pirenoforina
%A Everaldo F. Santos Filho
%A Italo Ricardo S. Araujo
%A Mirela Garcia
%A Jefferson L. Princival
%J Orbital : the Electronic Journal of Chemistry
%D 2012
%I Universidade Federal de Mato Grosso do Sul
%X Macrodiolides are macrocyclic compounds containing two ester groups in a cyclic chain. Of this class of compounds, Pyrenophorin (1) shows antifungal activity, and is produced from the pathogenic fungus Pyrenophora avenae. As this substance, derived from nature, is isolated in small quantities, an asymmetric synthesis using a simple and efficient methodology would be of great interest. The proposed synthetic route starts with the protection of propargyl alcohol 3 using DHP and feldspar as catalyst. Compound 5 obtained in this reaction was then subjected to acid-base reaction between the acetylenic proton and 1 eq. n-BuLi, leading to formation of the acetylide 5A. The 1,2- addition reaction between 5A and g-valerolactone (6) leads to the formation of alkinone 7 in 67% yield. Subsequently, compound 7 was subjected to a ketalization reaction using the same feldspar catalyst. Ketal 8 was formed under concomitant removal of the THP group. The product of this reaction (8) was then submitted to a reduction reaction of the triple bond to form olefin 9 with E configuration. Currently, the conditions for obtaining 10 by oxidation using Jones reagent, are being optimized. Compound 10,    obtained as described, is being subjected to a macrolactonization reaction. Various conditions including the use of enzymes are being studied. In addition, a study involving the enantioselective synthesis of (R,R)-(-)-pyrenophorin, using enzymatic kinetic resolution of the racemic mixture of compound 8, is in progress in the group : Macrodiol¨ªdeos s o compostos macroc¨ªclicos que apresentam em sua estrutura dois grupos ¨¦steres contidos em uma cadeia c¨ªclica. Dentre essa classe de compostos, a Pirenoforina (1) apresenta atividade antif¨²ngica, e ¨¦ produzida a partir do fungo patog¨ºnico Pyrenophora avenae. Como essa substancia, oriunda da natureza, ¨¦ isolada em pequenas quantidades, uma forma de s¨ªntese assim¨¦trica empregando uma metodologia simples e eficiente seria de grande interesse. A rota sint¨¦tica proposta inicia-se com a prote  o do ¨¢lcool proparg¨ªlico 3, empregando-se DHP e um catalisador neutro constitu¨ªdo por feldspato. O composto 5 obtido desta rea  o, foi ent o submetido ¨¤ rea  o ¨¢cido base entre o pr¨®ton acetil¨ºnico de 5 e 1 eq. de n-BuLi, levando a forma  o do acetileto 5A. A rea  o de adi  o 1,2- entre 5A e a g-valerolactona (6), leva a forma  o da alquinona 7 em 67 % de rendimento. Posteriormente, o composto 7 foi submetido ¨¤ rea  o de cetaliza  o empregando o mesmo catalisador de feldspato, onde se observa a forma  o do cetal 8, e remo  o do grupo THP do ¨¢lcool de form
%K s¨ªntese organica
%K macrodiol¨ªdeo
%K pirenoforina
%K catalisadores ¨¢cidos de feldspato
%U http://www.orbital.ufms.br/index.php/Chemistry/article/view/337