New syntheses of densely functionalized protected derivatives of 3-amino-3,6-dideoxyaminosugars have been accomplished in an efficient and straightforward manner. The key step of such approaches involves a highly stereoselective titanium-mediated aldol addition of a chiral α-bromo ketone, easily available from lactate esters, to crotonaldehyde. Further functional group transformations, including a new regioselective Staudinger–aza-Wittig reaction of an azidodiacetate, afford in a few steps and high yield the desired carbohydrates as advanced intermediates capable of participating in subsequent glycosylation reactions.
Organic & Biomolecular Chemistry
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