aldolisation reaction of lithium ester enolates with chiral α,β-epoxyaldehydes 2a–2f has been investigated. The reaction proceeds with diastereofacial preference in favour of the anti isomer (anti:syn ≈ 4:1) and can be greatly enhanced in the case of cis α,β-epoxy-aldehydes 2a–2c by a synergic effect of temperature and enolate excess (anti:syn 13:1). The Felkin-Ahn model can explain the results obtained
The stereochemistry of addition of lithiumenolates to the α,β-epoxyaldehydes 1z–3 has been investigated. Moderate to high diastereoselectivity (up to 13:1) is obtained in favour of the anti isomer, which is explained by the Felkin-Anh model for asymmetric induction.
The C(4-14) polyolic segment of antifungal macrolide strevertenes has been synthesized for the first time in protected form, incorporating four stereogenic centers. The synthetic strategy developed is based on the connection of two subunits prepared starting from the same chiral building block. (C) 2008 Elsevier Ltd. All rights reserved.