Sharpless dihydroxylation Claisen

In their short synthesis of ( - )-162, Pearson and Hembre also began with the protected D-erythronolactone derivative 197, which was converted in three steps into a mixture (97 3) of diastereomeric allylic alcohols 203 (Scheme 29) 127). Separation of the epimers, although possible, was not necessary as both alcohols yielded the same product 204 after Johnson orthoester Claisen rearrangement. Subsequent Sharpless asymmetric dihydroxylation with AD-Mix-p gave as major... 

Sharpless strategy is based on the very effective asymmetric dihydroxylation (AD-mix.-a or (3) of the y,5-unsaturated ester 140 to afford directly the desired (+) or (-)-muricatacin 19 with 95 and 96 % ee, respectively, and in 74 % overall yield from tridecanal 138 (Fig. 18). The ester 140 is obtained through a Claisen rearrangement of the allylic alcohol 139. 

---