Large‐Scale Synthesis of Crystalline 1,2,3,4,6,7‐Hexa‐ O ‐acetyl‐ L ‐ glycero‐ α‐ D ‐ manno ‐heptopyranose

The higher‐carbon sugar L ‐ glycero ‐ D ‐ manno ‐heptose is a major constituent of the inner core region of the lipopolysaccharide (LPS) of many Gram‐negative bacteria. All preparative routes used to date require multiple steps, and scalability has been rarely addressed. Here a highly practical synthesis of crystalline 1,2,3,4,6,7‐hexa‐ O ‐acetyl‐ L ‐ glycero ‐α‐ D ‐ manno ‐heptopyranose by a simple four‐step sequence starting from L ‐lyxose is disclosed. Only two recrystallisations are required and the process was demonstrated on a >100 mmol scale, yielding 41 g of the target compound.