2- Acetamido-2-desoxy-D-mannose

N-Acetybuuramhuc acid. I he yield and stereoselectivity of the aldol condensation of 2-acetamido-2-desoxy-D-mannose (I) with oxalaoetic acid (2) to give N-acctyl-neuraminic acid (.3) arc improved by adding sodium tetraborate to the reaction, which is carried out in aqueous solution at pHIO. Thus in the absence of borate ion, yields of (3) of 11.5 % have been reported, whereas addition of borate improves the yield to 21.6%. I he borate ion inhibits the alkaline epimerization of various 2-acylamino-2-dcsoxy-aldo.scs. 

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