AbstractThree homochiral polyhydroxylated piperidines containing a quaternary carbon branch at C‐2 of the heterocyclic ring, which can be considered as branched analogues of deoxymannorijimycin (DMJ), and their corresponding lactams were synthesised from readily available and versatile carbohydrate lactones containing a 2‐C‐hydroxymethyl branch. The key step in the synthesis of these iminosugars, 1,5‐dideoxy‐2‐C‐hydroxymethyl‐1,5‐imino‐D‐mannitol, 1,5‐dideoxy‐2‐C‐hydroxymethyl‐1,5‐imino‐L‐gulitol and 1,5‐dideoxy‐2‐C‐hydroxymethyl‐1,5‐imino‐D‐talitol, was an efficient modified Kiliani reaction performed on the readily available ketose starting materials L‐sorbose and D‐fructose. The introduction of the carbon branch at C‐2 resulted in loss of glycosidase inhibitory activity, which could be advantageous for therapeutic use of such compounds as chaperones.