Zearalenone dimethyl ether

Masamune has made use of this property for synthesis of medium ring lactones (macrolides), for example, zearalenone dimethyl ether ethylene ketal (5) from the hydroxy ester (4). On treatment with mercuric trifluoroacetate at 25°, (4) is converted within 5 min. into the lactone (5) in >90% yield (recrystalhzed). 

Mercuric trifluoroacetate [Hg(OCOCF3)2] is an effective reagent for the cyclization of hydroxy thio-esters. 5 This cyclization procedure was used by Masamune et al. for the conversion of 225 to 227 (in 90% yield) in a synthesis of zearalenone dimethyl ether. Masamune developed this procedure to complete the total synthesis of methymycin, where one step involved treatment of a thioester with mercuric salts. 2,96 Mercury(II) has an affinity for bivalent sulfur and it binds the thioester unit as well as the terminal hydroxyl... 

Thallium(l) thiolates have been introduced by Masamune et Their use is especially advantageous if 5-t-butyl thiocarboxylic esters are to be prepared which can serve as educts for macrolide synthesis. Zearalenone dimethyl ether ethylene acetal (22 cf. also Scheme 1) was obtained from the corresponding acid chloride and thallium(I) a-methylpropanethiolate via the S-f-butyl benzenecarbo-thioate (21 equation 14)... 

The final step in the synthesis of DL-zearalenone (2) involved removal of the protecting groups of the dimethyl ether (I). Treatment with boron trifluoride etherate or... 

In 1979, Tsuji s group [51] reported an alternative approach to macrolactonization. Inspired by their previous success in the preparation of recifeiolide and 9-decanolide, the authors envisioned that the dimethyl ether of zearalenone (6) could be obtained via olefination using the co-iodoalkyl phenylthioacetate 7 (Scheme 7.2). The Michael addition of diethyl malonate (11) to 10 followed by decarboxylation afforded an ethyl ester, which was reduced to alcohol and converted into the tosylate 12. Wacker-Tsuji oxidation of the terminal olefin was then followed by reduction of the ketone and conversion of the tosylate into iodide to provide 9. This was... 

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