64(P37) コンピュータを利用した立体化学構造解析決定手法(ポスター発表の部)

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For the determination of 3D molecular structure and absolute configuration (R/S) of natural organic compounds, an X-ray crystallography method is the most powerful technique. However, the method can not be used if a compound does not crystallize. A general technique for determination of the stereochemistry is the use of chemical reaction to decompose into small fragments for relating with the known compounds. If the both methods can not work, the NMR Distance Geometry Method, its appearance some ten years ago, that is an epoch-making method of analyzing the 3D molecular structure of protein in solution, can be used as an important method. The NMR Distance Geometry Method may be broadly classified into two optimization methods. The first is the method of taking three dimensional position relationships of each atom constituting the molecule as xyz variables of the Descartes coordinate system, is generally used. The second is the method of taking only the angle of rotation (dihedral angle) around the chemical bond in a dihedral angle coordinate system, in which the bond length of the bond between atoms in the molecule and bond angle are fixed, as the variable. The latter is the DADAS method (Distance Analysis in Dihedral Angle Space). This is used in the MolSkop as the DADAS90 program for calculations of molecular structure, using the constraint data of distance between atoms in a molecule obtained from the NMR data, the dihedral angle constraint data from the J spin-spin coupling constants. The DADAS90 can determine a stable molecular structure from the aspects of stereochemistry, thanks to the retention of chirality (R/S) even during the calculations for the optimum structure. The new technique, stereochemistry structure determination method used by computer, with the MolSkop system and a Chiral program that newly developed, applied to determine the stereochemistry of three cyclic natural organic compounds, cyclothiazomycin, sekothrixide and promothiocin. This technique can be also used for analysis of stereo structures of natural organic compounds, R/S determination, conformation analysis, and for steric positioning analysis of composite molecules.
1996-09-02

64(P37) コンピュータを利用した立体化学構造解析決定手法(ポスター発表の部)

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