Glycosyl Imidates, 42 Selectively Protected Lactose and 2‐Azido Lactose, Building Blocks for Glycolipid Synthesis

Performing regioselective alkylation at 3′‐OH of benzyl β‐lactoside 1 by the stannylation method we prepared the 3′‐OH‐ and 4′‐OH‐unprotected lactose derivatives 5 and 10 and the 4′‐OH‐unprotected lactose derivative 9 containing a different protecting group at 3′‐OH, suitable for further transformations. These building blocks are valuable glycosyl acceptors in glycolipid synthesis. For the synthesis of glycosyl donors with Gal(β1 → 4)GlcNAc‐structure we used the 2‐azido lactose derivative 19. By regioselective alkylation of 3′‐OH by the stannylation method and application of other common regioselective protecting procedures we prepared the trichloroacetimidates 17, 24, and 30 containing special protecting groups at 3′‐OH, 4′‐OH, and 6′‐OH which are suitable for further transformations in these positions.