Abstract
| - A synthesis of the C(29)−C(45) bis-pyran subunit 2 of spongistatin 1 (1a) is described. The synthesisproceeds in 19 steps from the chiral aldehyde ent-7, and features highly diastereoselectiveα-alkoxyallylation reactions using the γ-alkoxy substituted allylstannanes 17 and 19, as well as athermodynamically controlled intramolecular Michael addition to close the F-ring pyran. The Ering was assembled via the Mukaiyama aldol reaction of F-ring methyl ketone 3 and the 2,3-synaldehyde 4.
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