酮在秋水仙素與甲硫秋水仙素的光化學與光物理的研究

The study of the photochemical and photophysical properties of moiety “tropolone” in colchicine and thiocolchicine.

孫崇文(Chung-Wen Sun)

指導教授 ： 方泰山

國立臺灣師範大學/理學院/化學系/碩士(2002年)

摘要

無資料

關鍵字

酮 ； 秋水仙素 ； 甲硫秋水仙素 ； 量子效應 ； HASH(0xbe9c9ac)

並列摘要

The photochemical and photophysical properties of moiety “tropolone” in colchicine〈1〉and thiocolchicine〈5〉were studied. Irradiation of colchicine〈1〉in methanol gives mainly two photoproducts：β－lumicolchicine〈2〉andγ－lumicolchicine〈3〉. Further irradiation of β－lumicolchicine〈2〉in methanol gives the photoproduct ofα－lumicolchicine〈4〉. Irradiation of thiocolchicine〈5〉in methanol gives mainly two photoproductsβ－lumithiocolchicine〈6〉andγ－lumithiocolchicine〈7〉.
The low lying（π、π*） excited singlet state is responsible for the photochemistry of colchicine〈1〉and thiocolchicine 〈5〉 based on their UV-Vis absorption spectrum、fluorescence emission spectrum as well as fluorescence lifetime measurement.
In comparison of the quantum effect (ψ) of compound〈1〉and compound〈5〉 in different polarity solvents, the results of the 3 aspects are obtained as follows :
Ⅰ、the disappearance quantum yield of compound〈1〉：ψin methanol ≒ψin benzene.
（ψ〈1〉methanol＝－1.25×10-6, ψ〈1〉benzene＝－1.15×10-6）
Ⅱ、the disappearance quantum yield of compound〈5〉：ψin methanol ＜＜ψin benzene.
（ψ〈5〉methanol＝－4.90×10-9, ψ〈5〉benzene＝－6.66×10-8）
Ⅲ、the quantum yield of photoadducts β/γ ratio of compound〈1〉＞the quantum yield of photoadducts β/γ ratio of compound〈5〉.
（in benzene：β/γ〈1〉＝6.5, β/γ〈5〉＝2.1）
（in methanol：β/γ〈1〉＝13, β/γ〈5〉＝2.2）
The results of Ⅰand Ⅲ show that the photochemical mechanism of colchicine〈1〉is not affected by solvent polarity but by the molecular steric selectivity. This infers that the mechanism of colchicine〈1〉 favor Woodward－Hoffmann electrocyclic reaction. The results of Ⅱand Ⅲ show that the photochemical inactivity of thiocolchicine〈5〉is dominated by solvent polarity as well as the mesomeric effect of thiomethoxy group which can stabilize the charge transfer singlet excited state. So it is inferred that the mechanism of thiocolchicine〈5〉favors the concomitant charge separation of the excited singlet state of tropolone chromophore。
In summarize, results show that the key point of the photochemical behavior of mechanism of colchicine〈1〉and thiocolchicine〈5〉favors Woodward－Hoffmann electrocyclic concerted reaction due to the N-H—O bonded of moiety, tropolone, which is ended up with the 2+2（π, π*）single excited state energy transfer. The mechanism of colchine 〈1〉 favors the (2+2) electrocyclic concerted addition, whereas that of thiocolchicine〈5〉favor the concomitant charge separation of tropolone step-wised slower cycloaddition.

並列關鍵字

tropolone ； colchicine ； thiocolchicine ； quantum effect ； Woodward－Hoffmann

參考文獻

9、Laura Bussotti, Maurizio D’Auria, Paolo Foggi, Giordano Lesma, Roberto Righini and Alessandra Silvani,“The Photochemical Behavior of Colchicone and Thiocolchicone”,Photochemistry and Photobiology , 2000,Vol.71(1),pp29-34。

1、Jeffrey R. Peterson1 and Timothy J. Mitchison, “Small Molecules,Big Impact:A History of Chemical Inhibitors and the Cytoskeleton”,Chemistry & Biology,2002,Vol.9,pp1275-1285。

2、A. Cohen,J.W.Cook, and (Miss)E.M.F.Roe.,“Colchicine and Related Compounds.Part I Some Observations on the Structure of Colchicine.”J.Chem.Soc.(London), 1940,pp194-197。

3、R.Grewe, and W.Wulf, “Rudolf Grewe and Wilhelm Wulf:Die Umwandlung des Colchicines durch Sonnenlicht”, Chem.Ber.,1951,Vol.84,pp621-625。

5、Pete D. Gardner, Richard L. Brandon1 and G. Rufus Haynes2, “The Structure of β-and γ- Lumicolchicine. Ring-D Elaboration Products”J. Am. Chem. Soc., 1957,Vol.79,pp6334-6337。