RESUMO
The first asymmetric total syntheses of the real isolation product (2S,5R,8R)-greensporone F and (2S,5R,8R)-dechlorogreensporone F, 14-membered resorcylic acid lactones with a cis-2,5-disubstituted tetrahydrofuran ring system, was accomplished. The synthesis features a late-stage Lewis acid-catalyzed stereoselective intramolecular oxa-Michael reaction, E-selective ring-closing metathesis, De Brabander's esterification, and Jacobsen's hydrolytic kinetic resolution as the key steps. Synthesis of both real isolation and erroneously proposed structure necessitated the revision of the absolute configuration of greensporone F and dechlorogreensporone F. The erroneous representation of (2S,5S,8S)-configuration in greensporone F and dechlorogreensporone F was assigned to be (2S,5R,8R) by comparison with the NMR data and specific rotation of the synthetic compounds with that of the reported data.
RESUMO
The first asymmetric total synthesis and stereochemical assignments of 10-membered macrolactones relgro and 10'-oxorelgro are disclosed. To this end, palladium-catalyzed Stille coupling, the Mitsunobu reaction, ring-closing metathesis, EDCI promoted coupling and the Jacobsen hydrolytic kinetic resolution are used as key steps. The total synthesis followed by thorough evaluation of the optical rotation and CD spectral data led to the revision of the absolute configuration at C-6' for both relgro and 10'-oxorelgro. Moreover, the 1H as well as 13C NMR data are reported for the first time for relgro.
RESUMO
The stereoselective total synthesis of zeaenol and 7-epi-zeaenol is achieved in a convergent manner using Julia-Kocienski olefination, protecting group-directed intermolecular diastereoselective Nozaki-Hiyama-Kishi (NHK) reaction, De Brabander's lactonization reaction and CBS reduction as the key steps. In this article, we have observed the most suitable protecting groups with respect to selectivity during the protecting group directed intermolecular asymmetric Nozaki-Hiyama-Kishi reaction. The zeaenol, 7-epi-zeaenol and its derivatives were analyzed for their biological activity and screened in four cancer cell lines.