Alkylidenecarbene insertion at anomeric CH bonds. Synthesis of 3-deoxy-d-arabino-2-heptulosonic acid (DAH) and 3-deoxy-d-manno-2-octulosonic acid (KDO)

A novel method for the homologation of glycals to the corresponding 3-deoxy-2-ulosonic acids, based on the [1,5]-CH bond insertion of alkylidenecarbenes, is presented. The application of this approach is illustrated through the synthesis of 3-deoxy-d-arabino-2-heptulosonic acid (DAH) and 3-deoxy-d-manno-2-octulosonic acid (KDO).