N-Acetylglycine trimer, tetramer, pentamer, their potassium salts, and their N-deuterated derivatives have been prepared. Two crystalline modifications (solid-A and solid-B) have been obtained for acid-type molecules. The solid-A is more stable than the solid-B at room temperature. The solid-A Q solid-B conversion similar to the polyglycine I1 (PGII)* polyglycine I (PGI) conversion has been observed. The X-ray powder patterns and the ...