Maleimide is known to be one of the best model of DNA molecules. The photoreaction of the skin-sensitizing agents, 5,7-dimethoxycoumarin(DMC) and 8-methoxypsoralen (8-MOP), with maleimide is studied in order to elucidate the mechanism of the skin-photosensitization. The reaction was carried out in fluid chloroform solution and frozen state of dioxane solution. Reaction products were analyzed by TLC and the major product was isolated by column chromatography and preparative TLC. The structure of the photoproduct was characterized by the spectroscopic methods.
DMC-maleimide and 8-MOP-maleimide photoproducts were proved to be $C_4$-cycloadducts formed through the pyrone double bond and furan double bond respectively.
The fluorescence of DMC and 8-MOP was quenched by maleimide giving linear Stern-Volmer plot and $K_q$'s of 7.61×$10^9$, 7.56×$10^9$ l/mole/sec are obtained respectively. A singlet exciplex formation mechanism was proposed for the photocycloaddition reaction of DMC to maleimide. But the triplet mechanism seems to be better suited for the photoreaction of 8-MOP to maleimide.
말레이미드는 DNA분자의 가장 좋은 모델중의 하나로 알려져 있다. 피부광독성을 나타내는 5,7 -디메톡시쿠마린과 8-메톡시소랄렌의 말레이미드와의 반응이 피부광독성의 기작을 밝히기 위해 연구 되었다. 광반응은 $CHCl_3$ 용액 및 디옥산 얼린 상태에서 수행되었다. 반응생성물들은 TLC에 의해 분석되었고, 주 생성물이 대롱크로마토그래피와 preparative TLC에 의해 분리되었다. 광생성물의 구조는 분광학적인 방법에 의해 결정되었다.
DMC-말레이미드 및 8-MOP - 말레이미드 광생성물은 각각 피론 이중결합 및 푸란이중결합을 통한 $C_4$-고리화광부가물이었다.
DMC 및 8-MOP의 형광이 말레이미드에 의해서 ？칭되어, 직선관계를 주는 Stern-Volmer plot이 얻어졌고, 각각의 ？칭속도상수는 7.61 × $10^9$, 7.56 × $10^9$ l/mole/sec 이었다. DMC - 말레이미드의 광부가 반응은 singlet exciplex기작을 통해 진행되었고, 8-MOP 말레이미드의 광반응은 삼중상태 메카니즘도 유력하다.
