The intramolecular Diels−Alder (IMDA) reactions of C(8)-substituted decatrienoates have been studied. The stereospecific formation of 11 via an endo-boat-9 transition state attests to the powerful directing influence of a C(8) substituent in the IMDA of decatrienoate. In addition, the contrasting observations that stereospecific 9 f 11 occurs at room temperature while the nor-tert-butyl substrate (4a) requires 125 °C/5 h reaction conditions and produces a 60:40 mixture of diastereomers provide clear evidence that a bulky C(8) substituent is a powerful conformational activator of the IMDA. In the course of studies directed toward total syntheses of eleuthesides (e.g., eleutherobin, sarcodictyins), we have undertaken a study of the intramolecular Diels-Alder reaction (IMDA) 2 of decatrienoate systems (Figure 1). While both the Nicolaou 3 and Danishefsky 4 groups have reported total syntheses of eleutherobin, their strategies proceeded by elaboration of A-ring precursors (+)-carvone and (-)-phellandrene, respectively. Our objective was to develop eleutheside synthetic strategies that readily accommodate A-ring modification. We selected an IMDA route because in-depth analysis of the competing cycloaddition transition (1) (a) Presented at the 219th National Meeting of the American Chemical Society, San Francisco, CA, March 26-30, 2000; ORGN 343. (b) For a related study, see: Jung, M. E.; Huang, A.; Johnson, T. W.) (a) Hamel, E.; Sackett, D. L.; Vourloumis, D.; Nicolaou, K. C. Biochemistry 1999, 38, 5490-8. (b) Nicolaou, K. C.; Xu, J. Y.; Kim, S.; Pfefferkorn, J.; Ohshima, T.; Vourloumis, D.; Hosokawa, S. J. Am. Chem. Soc. 1998, 120, 8661-73. (c) Nicolaou, K. C.; van Delft, F.; Ohshima, T.; Vourloumis, D.; Xu, J.; Hosokawa, S.; Pfefferkorn, J.; Kim, S.; Li, T.
Kim, P., Nantz, M. H., Kurth, M. J., & Olmstead, M. M. (2000). Intramolecular Diels-Alder and Alder Ene Reactions. Org. Lett., 2, 1831–1834. Retrieved from https://pubs.acs.org/sharingguidelines