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Abstract
A convergent aromatic annulation strategy based on the Michael addition of the dimethyl-1,3-acetonedicarboxylate 1 anion to 2-hexynal 2, followed by a regiocontrolled Dieckmann-type cyclization, has been applied to a total synthesis of the antibiotic, DB-2073 I. This tandem annulation reaction generates the fully substituted aromatic intermediate 3, which was transformed by a five-step sequence to I.
In recent years we have developed a total and a formal synthesis of mycophenolic acid [Covarrubias-Zúñiga, A.; González-Lucas, A. Tetrahedron Lett. 1998, 39, 2881; Covarrubias-Zúñiga, A.; Díaz-Domínguez, J.; Olguín-Uribe, J.S. Synthetic Communications 2001, 31, 1373.] using as key step tandem reactions based on Michael addition and intramolecular Dieckmann-cyclization; In this article we utilize this synthetic approach for the total synthesis of the resorcinol DB-2073 I. This tetrasubstituted resorcinol was isolated and purified from pseudomonas B-9004, showing antibacterial and antifungal activities [Kanda, N.; Ishizaki, N.I.; Oshima, M.; Handa, A.; Kitahara, T.J. Antibiotics 1975, 28, 935.]. The molecular formula of DB-2073 was established by spectroscopic methods [Kitahara, T.; Kanda, N. J. Antibiotics 1975, 28, 943.], as 2-hexyl-5-propyl-resorcinol I.
Acknowledgments
This research was supported by a Grant-in-Aid for Scientific Research No. 27610-E from CONACYT, México. The authors thank Dr. N. Zúñiga for helpful discussions, We thank Messrs. R. Gaviño, R. Patiño, L. Velasco, and F. J. Pérez for running the spectra.