Carbohydrate aziridines reactions

The purpose of this chapter is to present the chemistry of carbohydrate aziridines, with the emphasis being placed on surveying preparative methods and ring-opening reactions. We have omitted spiroaziridines and alditol-based aziridines from this chapter. Literature has been surveyed up to the end of 2003. The chemistry of carbohydrate aziridines has not yet been treated in a specialized article. 

The aziridine-ring closure based on the Mitsunobu reaction, the Staudinger reaction, and isomerization of aminooxiranes also involves nucleophilic displacement as the key step of the reaction mechanism. Other reactions rarely reported in the synthesis of carbohydrate aziridines involve nonstandard, " even unusual procedures lacking a general application. 

A vast majority of the amino derivatives used as substrates in the synthesis of carbohydrate aziridines are A-substituted, mostly as A-acylamines or A-aryl(alk-yljsulfonylamines. Reaction of free amines has rarely been reportedin the carbohydrate field and difficult and incomplete cyclization was generally encountered. Paulsen and Stoye, however, reported spontaneous cyclization of 6-hydrazino-5-C-mesyl-D-hexofuranoses, obtained from 5,6-di-C-mesyl-hexofura-noses by treatment with hydrazine, into the A-amino-5,6-epimino derivatives." ... 

At that time, as now, the enantiomers of many chiral amines were obtained as natural products or by synthesis from naturally occurring amines, a-amino acids and alkaloids, while others were only prepared by introduction of an amino group by appropriate reactions into substances from the chiral pool carbohydrates, hydroxy acids, terpenes and alkaloids. In this connection, a recent review10 outlines the preparation of chiral aziridines from enantiomerically pure starting materials from natural or synthetic sources and the use of these aziridines in stereoselective transformations. Another report11 gives the use of the enantiomers of the a-amino acid esters for the asymmetric synthesis of nitrogen heterocyclic compounds. 

Herein an overview of the most relevant approaches for the synthesis of un-natiual heterocycles of biological and industrial potential from carbohydrates is presented the natiual heterocycles have been previously reviewed [6]. This review is hmited to heterocycles with one or more of their carbon skeletons derived from carbohydrate precursors—those formed by cycloaddition reactions are not included. Also, carbohydrates with strained ring systems, oxiranes, aziridines, and thiiranes have aheady been reviewed and are not included herein [20]. The synthetic approaches for the reviewed heterocycles are divided according to the size of the heterocychc rings and the number of hetero atoms in the ring. The bicyclic ring systems are included under the smaller ring of their skeleton. 

---