Variations in the lattice arrangement and the tendency toward isomorphic behavior in a group of trans-β2,3 amino acid derivatives with Boc and oxazolidinone moieties at the N- and C-terminals are discussed. The substitution pattern at the α- and β positions in these systems was found to give different torsional preferences and hence different molecular organizations in their crystals. Analysis of such preferences in their azide analogs has unraveled the involvement of a relatively uncommon carbonyl-azide dipolar interaction in lattice stabilization. © 2010 American Chemical Society.