Allylic dactylolide synthesis

In the final step of this total synthesis, diol 35 is subjected to Dess-Martin periodinane (69), involving the oxidation of both the primary and the allylic alcohol and consequently removing the redundant C-7 stereogenic center to afford (-)-dactylolide (-)- as a single diastereo-mer. 

Scheme 18.66 Seleno Mislow-Evans applied for allylic transposition in total synthesis of i+i-dactylolide.—...

Shortly after the synthesis by Floreancig group. Keck and co-workers completed the synthesis of (+)-dactylolide. Retorosynthetically, Keck s approach to dac-tylolide is similar to those of previous syntheses, in that the major disconnection at C(2)-C(3) at the late stage macrocyclization is to be achieved through Horner-Wadsworth-Emmons olefination and the Prins cyclization via an allyl silane addition to an aldehyde to build up the 2,6-cw-tetrahydropyran unit (Scheme 2.57). However, preparation of the homoallyl alcohol 2.274 fragment via Keck s asymmetric aUylation is unique as illustrated in Scheme 2.58. 

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