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Enantioselective Synthesis of the Spiroketal Unit of Milbemycins and 22,23-Dihydroavermectins by J.P. Férézou; J. Gauchet-Prunet; M. Julia; A. Pancrazi is a Chemistry article available to read on EtoBox.

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## w : The crystalline spiroketal sub-unit 2 has been synthesized in ten steps from the 2S,3Rdiol2 using a remote partial stereocontrol for the aldolisation step. The unique biological activity of milbemycins and avermectins as well as their challenging structural features (1) led us to develop a program towards their synthesis (2). Numerous routes to the spiroketal moiety of these molecules have been reported (3). Our approach of the spiroketal system of milbemycins and 22,23\_dihydroavermectins (b series) involved a stepwise condensation at both ends of 2,4-pentanedione 1 as shown on the Scheme (2a). This letter presents an enantioselective synthesis of the subunit 2 using a remote stereocontrol for the crucial aldolisation reaction. Previous work had shown the possibility of controlling the chiral center at C-21 (4) by use of a suitable synthon affording the correct stereochemistry at C-24 and C-25. Control of the C-17 center of 2 was next investigated.

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Author

J.P. Férézou; J. Gauchet-Prunet; M. Julia; A. Pancrazi

Publisher

Elsevier Science; Elsevier ; Elsevier Ltd.; Elsevier BV (ISSN 0040-4039)

Published

1988

Language

EN

Field

Chemistry (Physical Sciences)