Synthesis of polyacetylenic acids isolated from Nanodea muscosa Diego Alves, Cristina W. Nogueira and Gilson Zeni * Laborato ´riodeSı ´ntese, Reatividade, Avaliac ¸a ˜o Farmacolo ´gica e Toxicologica de Organocalcoge ˆnios, CCNE, UFSM, Santa Maria, Rio Grande do Sul, CEP 97105-900, Brazil Received 21 September 2005; revised 29 September 2005; accepted 11 October 2005 Available online 27 October 2005 Abstract—The first total synthesis of two linear polyacetylenic compounds is described. The synthesis of (E)-octadec-13-en-11-ynoic acid 1 and (E)-octadec-13-en-9,11-diynoic acid 2 by using the vinylic telluride coupling reaction was accomplished. Ó 2005 Elsevier Ltd. All rights reserved. Several examples of acetylenic and polyacetylenic compounds have been isolated in recent years. 1 Many of these natural products have shown biological activi- ties ranging from antibacterial, fungicidal and in vitro antitumor properties to cell division inhibition. 2 In addition, these compounds could also be potent inhibi- tors of the arachidonic acid metabolism. 3 Recently, two new linear polyacetylenic acids [(13E)-octadec-13- en-11-ynoic acid] 1 and [(13E)-octadec-13-en-9,11-diy- noic acid] 2 (Fig. 1) were isolated from the aerial parts of Nanodea muscosa, a small herb found in extreme southern regions of South America. 4 These authors also elucidated the structure of compounds 1 and 2 by spectroscopic methods and assigned their absolute stereochemistry. In a previous work, we have already reported the syn- thesis of polyacetylenic acids isolated from Heisteria acuminata, utilizing, as a tool, the tellurium chemistry. 5 Many different classes of organotellurium compounds have been prepared and studied to date, vinylic tellu- rides are certainly the most useful and promising com- pounds in view of their usefulness in the organic synthesis. 6 In addition to their utility in the field of organic chemistry, toxicological and pharmacological aspects of organotellurium compounds have also been recently reviewed. 7 However, the use of tellurium chemistry for the syn- thetic organic chemists or as a tool in organic synthesis has been hampered due to a bad reputation related to the bad smell, toxicity or instability of these compounds. In fact, these comments are correct to a particular group of the tellurium compounds, but they are not a rule for all tellurium compounds. In our lab, we have used a lot of different classes of tellurium compounds and observed that tellurides or ditellurides, bearing an alkyl group with a low molecular weight, present a bad smell. Conversely, when these alkyl groups present any addi- tional substituent, the corresponding tellurides or ditel- lurides are practically odorless. Other tellurium compounds, such as trihalides, diaryl tellurides and ditellurides are solid, very stable (can be stored in the lab in a simple flask for a long time) and completely odorless. In addition, the vinylic tellu- rides, one of the most used classes of tellurium com- pounds, containing an aromatic, aliphatic saturated or unsaturated chains, which are odorless compounds, can be easily prepared, purified and stored as a com- mon chemical used in the lab. Another reason that has hindered the development of the organotellurium chem- istry is that the toxicological studies are still scarce in the literature, however, they are meant. Some authors have 0040-4039/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2005.10.032 Keywords: Vinylic tellurides; Palladium cross-coupling; Polyacetylenes; Enynes. * Corresponding author. Tel.: +11 55 55 220 8140; fax: +11 55 55 220 8031; e-mail: gzeni@quimica.ufsm.br COOH 1 2 COOH Figure 1. Tetrahedron Letters 46 (2005) 8761–8764 Tetrahedron Letters