Synthetic studies toward potent cytostatic macrolide bryostatin: an expedient synthesis of C1-C10 fragment

The stereoselective synthesis of C1-C10 fragment of cytostatic macrolide bryostatin is described. Two of the three chiral centers have been established via the Sharpless kinetic resolution of racemic allylic alcohol 15 followed by regioselective reduction of epoxy alcohol 8 with Red-Al. Diastereoselective Aldol reaction of an aldehyde 7 with methyl isobutyrate affords the corresponding β-hydroxyester 23 which is then transformed into tetrahydropyran ring system 3 via an intramolecular hemi-ketalization.