| Abstract
| - Rutamycin B (2) was synthesized from three principal subunits, spiroketal 75, keto aldehyde 83,and aldehyde 108. First, triol 62 was assembled by Julia coupling of sulfone 56 with aldehyde 58followed by an acid-catalyzed spiroketalization. The three hydroxyl functions of 62 were successfullydifferentiated, leading to phosphonate 75. The latter was condensed in a Wadsworth−Emmonsreaction with 83, prepared in six steps from (R)-aldehyde 76, to give 92. Coupling of the titaniumenolate of 92 with 108 afforded Felkin product 109 with high stereoselectivity in a process that iscritically dependent on the presence of the p-methoxybenzyl ether in the aldehyde. Transformationof 109 via aldehyde 116 to vinylboronate 122 was followed by macrocyclization under Suzukiconditions to yield 123. Exhaustive desilylation of the latter yielded rutamycin B.
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