Syntheses of 2-Amino-2-deoxy-aldoses

An account of the methods of synthesis of amino sugars has been given in an earlier Volume of this Series1 attention is devoted in this Section to methods recently developed. Several general methods have been employed for the synthesis of 2-amino-2-deoxy-aldoses these respectively involve direct amination of suitable sugar derivatives, interconversion of sugar series, and ascent or descent of a series with or without concomitant amination or molecular rearrangements. 

The Fischer-Leuchs synthesis of 2-amino-2-deoxy-D-gluconic acid9 (by hydrolysis of the corresponding nitrile, produced on addition of hydrogen 

R = alkyl or —CH2—COjEt [Et ester is hydrolyzed during reaction] 

An N-alkyl group is not removed under the reaction conditions, and an iV-substituted 2-amino-2-deoxy-aldose is formed. Under the same reaction conditions, anA-benzyl group is cleaved (with the uptake of a further mole of hydrogen per mole), to give the free 2-amino-2-deoxy-aldose and toluene  

Certain exceptions to this general scheme have been noted in which the normal hydrogenation of the nitrile group has not taken place. In these cases, a hydrolytic reaction has occurred, with the formation of an aldonic acid instead of the expected aldose.12 The anomalous reaction occurs when the nitrile exists in the (isomeric) iminolactone form for example, compound I is hydrolyzed directly, before hydrogenation can take place. This isomerism of the aldononitriles was established by Papadakis and Cohen,16 and the cyclic structure I was postulated by Wolfrom and coworkers.108 

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