STEREOELECTRONIC EFFECTS IN HYDROXYLATED SATURATED HETEROCYCLES

摘要

Six-membered hydroxylated saturated heterocycles show a plethora of steric and stereoelectronic effects: Perlin effect, anomeric and exoanomeric effects, reverse anomeric effect, gauche (or 1,3-diaxial) interactions, etc.[1] An interesting case occurs in some derivatives of 2-amino-2-deoxyaldoses: while their enamines (1,2) exist prevalently as a-anomers, their iminic counterparts (3,4) display ss-configuration at the anomeric center. Both behaviors have been widely exploited in synthetic carbohydrate chemistry, as the anomeric configuration can easily be preserved through such derivatives. So far, however, no satisfactory explanation has been provided.[2]