(3R,6R)-3-Benzyl-8-thia-1,4-diazabicyclo[4.3.0]nonane-2,5-dione, C13H14N2O2S

Abstract

Abstract.M r = 262.3, orthorhombic, P21212~, Z = 8, a = 9.256(2), b = 10.154(2), c --27.420 (8)A, D c = 1.352 Mg m -3. R w = 0.039 for 1546 reflections with I > 2.5a(I), out of 3190 independent measurements. The benzyl group is a (pseudo-)axial substituent on the diketopiperazine ring and is folded above this ring in such a way that the overall distance is equal to the sum of the van der Waals values. The piperazine ring has a boat-like form. The molecules in the crystal occur as dimers formed through two hydrogen bridges. The geometry of the compound, also called cyclol-D-Phe-L-(yS) Pro-], is compared to cyclo (-D-Phe-L-Pro-).

(3S,6S)-3-Isopropyl-1,4-diazabicyclo[4.4.0]decane-2,5-dione, C11H18N2O2: Bayesian statistics in data analysis

“…Bond distances and valence angles are given in Table 3. They are similar to values found in analogous derivatives (Ramani, Sasisekhara & Venkatesan, 1977;Van Poucke & Lenstra, 1982a,b;Van Poucke, Geise & Lenstra, 1983;Dillen & Lenstra, 1983). Endocyclic torsion angles and ring puckering parameters (Cremer & Pople, 1975) are presented in Table 4.…”

“…A parameter of interest to NMR spectroscopists, the angle between the C(3)C(2)N(1)C(6) and C(3)N(4)-C(5)C(6) planes, is 13.0 (5) and 13-3 (5) ° for the two crystallographically independent molecules. A pyramidal configuration around the peptide N(1) atom has been observed in a number of dipeptides (Sletten, 1970;Pattabhi, Venkatesan & Hall, 1973, 1974Van Poucke & Lenstra, 1982a,b), whereas the planar configuration seems to occur less frequently (Van Poucke, Geise & Lenstra, 1983;Dillen & Lenstra, 1983). In the title compound N (1) is insignificantly [0.024 (4) and 0.042 (4)A for the two molecules] out of the C(2)C(6)C(10) plane.…”

“…Typical aspects are the shape of the DKP ring, the type of fusion of the two rings, the conformation of the valanyl residue and the planarity near N(1). The X-ray determination reported here is one of a series (Dillen & Lenstra, 1983;Van Poucke, Geise & Lenstra, 1983;Van Poucke & Lenstra, 1982a,b), the reports of which should be useful in the interpretation of NMR spectra and chemical activity.…”

(6S)-1,4-Diazabicyclo[4.4.0]dec-8-ene-2,5-dione monohydrate, C8H10N2O2.H2O

“…Bond lengths and valence angles, listed in Table 2, are similar to values found in analogous derivatives (Ramani, Sasisekhara & Venkatesan, 1977;Van Poucke & Lenstra, 1982a,b;Van Poucke, Geise & Lenstra, 1983). The piperidine ring has a half-chair conformation, while the DKP ring has a shallow twist-boat form with the pseudo twofold axis passing through the keto functions.…”

“…A pyramidal configuration around the peptide N(1) atom in a number of dipeptides has been observed (Sletten, 1970;Pattabhi, Venkatesan & Hall, 1973, 1974Van Poucke & Lenstra, 1982a,b), whereas the planar configuration seems to occur less frequently (Van Poucke, Geise & Lenstra, 1983). In the title compound N(1) is insignificantly (ca 0.045/k) above the C(2)C(6)C(10) plane.…”