Short total syntheses of both the putative and actual structures of the clerodane diterpenoid (+/-)-sacacarin by double annulation.

R B Grossman, R M Rasne

Index: Org. Lett. 3(25) , 4027-30, (2001)

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Abstract

[reaction: see text] The putative structure of the naturally occurring clerodane diterpenoid (+/-)-sacacarin has been prepared in only 10 steps, six of which are C-C bond-forming steps, in a chemo-, regio-, and diastereoselective manner. The key part of the synthesis is the double annulation (double Michael, Pinner, and Dieckmann reaction) of a tethered carbon diacid and 3-butyn-2-one. A corrected structure for sacacarin is proposed, and the structure is proven by synthesis.