Chiral auxiliaries asymmetric metathesis

Based on the letrosynthetic analysis presented above, the first critical task on the way to testing the olefin metathesis-based strategy for the total synthesis of epothilone A (1) was the construction of the three key building blocks 61, 63, and 64. Focusing our attention first on the preparation of aldehyde 64, the Nicolaou group developed several approaches to this building block based on asymmetric synthesis with chiral auxiliaries one of these solutions is detailed in Scheme 19. 

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