The indium-mediated allylation reaction is a powerful tool for the elongation of carbohydrates since it can be performed in aqueous media under mild conditions [1,2]. We utilized this reaction in the synthesis of carbohydrate scaffolds containing the 3-deoxy-2-ulose motif, a barely investigated compound class [3]. The stereoselective outcome can be controlled by the presence or absence of a chelating group in α-position to the reacting carbonyl function as we verify on two model substrates [4,5]. Our approach towards the synthesis of 3-deoxy-D glycero-D-galacto-2-nonulose - the ketose analogue of widely distributed 2-keto-3-deoxy-D-glycero-D-galacto-nonoic acid (KDN) - is accompanied by demanding epimer separation which has been tackled by the introduction of an UV-active group attached to the allyl building block facilitating detection using HPLC. Synthetic as well as experimental details will be presented.
Scheme: Application of the indium-mediated allylation reaction in the synthesis of 3-deoxy-2-uloses and tackling of demanding epimer separation.
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