D-Altruronic acid

D-Altruronic acid, I, 67, 68 Aluminum chloride, in orthoacyl chloride formation, I, 119... 

Amino-2-deoxy-L-altruronic acid X D-ga/aclo-N2AE5... 

Actually, this reasoning lay behind the first observation of the anomeric effect. Similar stabilization of the reaction intermediates by the anomeric effect explains, qualitatively, the kinetics of conversion of derivatives of ) -D-galacturonic acid into the corresponding a-L-altruronic acid derivatives. Hydrolysis of the a is a few times faster than that of the fi anomer of aryl glycosides, and this can probably be explained similarly. In this case, the hydrolysis is affected by the initial, proton-transfer equilibrium. Because of the reverse anomeric effect, the relative stability of the resulting conjugate acids is reversed with respect to the neutral molecule, and the anomer is the more stable. This means that the reactivity of the axial anomer of the conjugate acid increases (and vice versa for the equatorial anomer). 

---