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20.6.1.4.2 Variation 2: The Masamune Method

DOI: 10.1055/sos-SD-020-01369

Maier, M. E.Science of Synthesis, (2007201459.

This procedure is based on the activation of S-tert-butyl esters of hydroxy acids. With thiophilic mercury(II) trifluoroacetate, the lactonization takes place in dilute acetonitrile solution at room temperature. A certain disadvantage is the fact that the conversion of the carboxylic acid into the corresponding thiol ester requires thallium(I) thiolates that react with the mixed anhydride formed from the carboxylic acid and diethyl chlorophosphate.[‌156‌] Cyclization of the zearalenone seco acid ketal proceeds very efficiently under these conditions (Scheme 55).[‌157‌] In a more complex setting (12-membered macrolide), however, the yield is rather moderate.[‌158‌]

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