Nucleophile epimine reaction

Neighboring group participation involving acylamino or acyloxy groups is common in nucleophilic substitution. For example, in the reaction of methyl 4,6-0-benzylidene-2-deoxy-2-benzoylamino-3-O-mesyl-a-D-altro-pyranoside 8 with NaOEt, no 3-0-ethoxy-mannoside derivative was obtained. Instead, oxazoline 9 and epimine 10 were identified in this reaction (O Scheme 5) [12]. This results from the l,2-tra 5 -diaxial relationship between the leaving... 

Most epimino sugars are relatively stable in neutral or basic conditions. They are usually stable in the presence of such hydride reductive reagents as lithium aluminum hydride or sodium borohydride. They tend to undergo cleavage reactions or decompose in the presence of acids. A-Acylated aziridines are prone to lose the A -acyl substituent in the presence of nucleophiles and bases, and caution must be taken when nucleophilic cleavage of the aziridine ring of N-acylated epimines is to be performed. 

For reactions of furanoid epimines, the configuration of the epimine does not determine the regioselectivity. Other factors, such as steric interactions between nucleophile and epimine, or soft or hard character of the nucleophile, may control the regioselectivity. 

Epimines of the u-galacto, D-allo, and D-talo configurations have been treated with analogous nucleophiles as for the 2,3-epimines, and their cleavage reactions are summarized in Tables XII, XIII, and XIV. 

Dauban and coworkers published a detailed study on the reactivity of 2,3-epimino-2,3-dideoxy-D-lyxono-1,4-lactone derivatives 370, 380 with both soft (RSH, AcOH, LiBr) and hard (ROH, BnNH2) nucleophiles. Reactions of the epimines with soft nucleophiles proceeded by direct aziridine-ring cleavage to give predominantly C-2 regioisomers. 

In a series of papers,Saeki and coworkers described cleavage reactions by nucleophiles of 5,6-epimines derived from hexofuranosides or hexo-furanoses, and 6,7-epimines derived from heptopyranoses. 

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