ChemInform Abstract: An Approach to the Synthesis of the C(17)-C(27) Fragment of Bryostatins

The organolithium reagent generated from the vinyl iodide 8 reacts with aldehyde 13 to give a mixture of the anti- and syn-silyloxy alcohols 14 and 15 together with the regioisomeric syn-silyloxy alcohol 16, ratio 14 : 15 : 16 = 4 : 1 : 1. The major anti-alcohol 14 was taken through to the methoxyacetal 27 so confirming this strategy for the stereoselective synthesis of the C(17)–C(23) fragment of bryostatins. The diol 30, which has configurations at each of its three chiral centres corresponding to the C(23)–C(27) fragment of bryostatins, was prepared in two steps from the aldehyde 28 and converted into the vinylstannane 45.