Trifluoroacetimidate preparation

Glycosyl trifluoroacetimidates have recently been introduced as glycosyl donors [321]. The compounds are prepared by the reaction of the hemiacetal hydroxyl group with N-substituted trifluoroacetimidoyl halides 138, providing anomeric mixtures of the imidates 139 (Scheme 4.24). 

The utility of glycosyl trifluoroacetimidates was demonstrated in the preparation of saponins. The synthesis of dioscin 146 [322] is shown in Scheme 4.25. As illustrated, diosgenin... 

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