CRYSTAL AND MOLECULAR STRUCTURE OF L-CIS-3,6-DIMETHYL-2,5-PIPERAZINEDIONE (L-ALANYL-L-ALANYL-2,5-DIKETOPIPERAZINE)

The crystal structure of L‐cis‐3, 6‐dimethyl‐2,5‐piperazinedione (L‐alanyl‐L‐alanyl‐2,5‐diketopinerazine) has been determined. The unit cell is triclinic with a = 8.05, b = 6.08, c = 5.15 Å, α = 131.7°, β = 82.4°, γ = 106.6°. The space group is P1 with one molecule per unit cell. The six‐membered ring is found to be nonplanar with an angle between the two amide group planes of 26°. One amide group deviates slightly from planarity. The experimental molecular model is discussed in terms of its flexibility. Copyright © 1969 John Wiley & Sons, Inc.