Synthesis of imino sugar scaffolds for the generation of glycosidase inhibitor libraries

We have synthesized imino sugar scaffolds bearing two points of diversity - the stereocenters located in α positions relative to the nitrogen atom - and three points of orthogonal derivatization - a carboxylic function, the primary hydroxy group, and the ring nitrogen atom. The key steps in the synthetic approach are the chain elongation of aldehyde 5 with the formation of an α,β-unsaturated ester, the Michael addition of an amine, and the final cyclization. This strategy leads to the preparation of different N-substituted imino sugar analogues having both α and β structures and of both D and L stereochemistry. Different derivatives have been prepared from the scaffolds we obtained. The carboxymethyl group was coupled to the amino function of different amino acids to afford compounds 30-34, while the selectively accessible primary hydroxy group has been substituted with an azido group to afford compounds 24-26. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.