Flexibility of supposed "rigid" molecules: substituted 2,5-piperazinediones (diketopiperazines).
The relevant results of accurate X-ray analyses of both the trans-and the L-cis-3,6-dimethyl-2,5-piperazinediones (diketopiperazines) are reported. We note that a large variability of conformations for the ring system can be accomplished by coupling small bond-angle deformations with large variations of the internal rotation angles. The experimental molecular models are discussed in terms of these changes and in terms of nonbonded intramolecular interactions.
Benedetti
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E
POLYMER RESEARCH INSTITUTE, POLYTECHNIC INSTITUTE OF BROOKLYN, NEW YORK.
Corradini
P
P
Goodman
M
M
Pedone
C
C