Structure and absolute configuration of the alkaloid clivorine

Chemical reaction paths. IV. Aspects of O.C = O interactions in crystals

“…It is possible that this lacuna is due to an unfortunate choice of examples -after all, we have relied on the more or less unsystematic provision of data and have no example of a transannular O...C=O interaction in an eight-membered ring comparable to the N...C=O interaction in clivorine (d= 1.993 A! Birnbaum, 1972). However, there is also the possibility that this gap occurs because O...C distances in the intermediate range 1.5-2.5 A would correspond to unfavourable interaction energies.…”

Molecular mechanics study of transannular amine-ketone (N?C(DOUBLE BOND)O) interaction in medium-sized heterocycles

“…Table I summarizes the results obtained for test molecules 3 and 4 using different force fields as compared to the crystal structures obtained by X-ray crystallography. 20,21 From each dynamics or conformational searching run two conformations were picked: the conformation of minimum energy and the conformation of minimum distance across the medium-sized ring between the nitrogen and the carbonyl carbon.…”

“…The fractional X-ray coordinates of the test molecules cryptopine and clivorine were typed in from the original references. 20,21 All molecules modeled were also sketched, converted into 3-Ž . dimensional 3-D structures, and minimized to the closest local minimum using the MSI software.…”

Structure and absolute configuration of (+)-doronine–benzene (1:1), C21H30ClNO8.C6H6

“…The final atomic coordinates, equivalent isotropic thermal parameters and their estimated standard deviations are listed in Table 1. * The orientation of the eight-membered ring in (+)-doronine is very similar to those of senkirkine (Birnbaum, 1974) and clivorine (Birnbaum, Klasek, Sedmera, Snatzke, Johnson & Stantavy, 1971;Birnbaum, 1972). It assumes a conformation in which one half, consisting of C(1), C(2), C(3), N(4) and C (8) (Sutton, 1965).…”

“…The three atoms bonded to C(8) and the transannular N are arranged nearly tetrahedrally around the C atom, indicating that hybridization at C(8) is intermediate between sp 2 and sp3; the mean bond angle at C(8) is 107.2 °. The extent of the partial bond N...C=O in the present structure may be compared to those found in clivorine (Birnbaum, 1972)and senkirkine (Birnbaum, 1974): the N...C(=O) distances are 1.993 and 2.292 A respectively, and the C=O bond lengths are 1.258 and 1.213/I, respectively. The transannular interaction between the carbonyl group and the tertiary amino function in (+)-doronine is significantly'weaker than the one in clivorine but slightly stronger than that in senkirkine.…”