Absorption Characteristics and Quantum Yields of Singlet Oxygen Generation of Thioguanosine Derivatives. (31st March 2018)

• Record Type: Journal Article
• Authors: Miyata, Shoma; Yamada, Takeshi; Isozaki, Tasuku; Sugimura, Hideyuki; Xu, Yao–Zhong; Suzuki, Tadashi
• Is Part Of: Photochemistry and photobiology. Volume 94:Number 4(2018)
• Page Start: 677
• Page End: 684
• Publication Date: 2018-03-31
• Subjects: Photochemistry -- Periodicals; Light -- Physiological effect -- Periodicals; 541.35
• DOI: 10.1111/php.12900
• Languages: English
• ISSNs: 0031-8655

Abstract

Abstract: 6‐Thioguanine (1a) is considered to be photochemotherapeutic due to its specific characteristics of photosensitivity to UVA light and singlet molecular oxygen generation. To extend its phototherapeutic ability, two related thioguanines, 8‐thioguanine (2a) and 6, 8‐dithioguanine (3a), have been designed and explored. Since the solubility of these thioguanines in dehydrated organic solvents is too poor to study, their triacetyl‐protected ribonucleosides, that is, 2′, 3′, 5′‐tri‐ O ‐acetyl‐6‐thioguanosine (1c), 2′, 3′, 5′‐tri‐ O ‐acetyl‐8‐thioguanosine (2c) and 2′, 3′, 5′‐tri‐ O ‐acetyl‐6, 8‐dithioguanosine (3c) were prepared and investigated. The absorption maxima of 1c, 2c and 3c in acetonitrile were found at longer wavelengths than that of unthiolated guanosine (4c). Especially, 3c has the longest wavelength for absorption maximum and the highest value in terms of molar absorption coefficient among all thionucleobases and thionucleosides reported. These absorption properties were also well reproduced by quantum chemical calculations. Quantum yields of singlet oxygen generation of 2c and 3c were determined by near‐infrared emission measurements to be as large as that of 1c. These results suggest that the newly synthesized thioguanosines, in particular 3c, can be further developed as a potential photosensitive agent for light‐induced therapies. Abstract : Three triacetyl‐protected thioguanosines, 6–thioguanosine, 8–thioguanosine and 6, 8–dithioguanosine have been prepared and explored to extend those phototherapeutic ability. These thioguanosines, especially 6, 8–dithio–derivative, have a good potential as a photosensitizer for photochemotherapy.