| Summary: | 碩士 === 國立成功大學 === 化學系碩博士班 === 91 === We discuss the conformations of cycloalkanes(C12H24、C14H28、C16H32、C18H36、C20H40) and the relations between conformations and biochemical activities of both Epothilones and Macrolides by semi-emprcial AM1 quantum mechanical calculation methods with PC-SPARTAN.
The calculation results show that the torsional energy of C-C bond in cycloalkanes is so low, even lower than 20 kJ/mol, reveals cycloalkanes are easily affected by external force so as to occur many conformation variations.
In conformation, only dihedral angle locating the torsional position changes larger than any other positions where is less affected. The cyclopropyl C-C bond has the larger torsional energy than usual ones, which means the conformation near cycloprpyl is more rigid, and not too easily be changed.
For cycloalkanes, the results of conformational analysis indicate that the simultaneous torsions of several dihedral angles can move the arrangement of carbon atoms in cycloalkanes. Despite the variation is not so apparent, the C-H bonds oscillate for the torsion of C-C bond. Those cyclopropyl cycloalkanes can fasten the local conformation of cycloalkanes, so that the oscillating angles of C-H bonds near cyclopropyl would be smaller.
From the conformation analysis of medicines, the flapping range of the side chain and functional groups in the medical cyclopropyl compounds would reduce largely because of the rigid cyclopropyl local conformation. Compared with the large flap of other conformations' medical side chain and functional groups, those which get cyclopropyl conformations in them are the medical compounds whose side chain and functional groups react with the active center much possibly. We think this is the main reason which results the difference of activities of medicines.
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