Synthesis, Photochemical Properties, and Cytotoxicities of 2H-Naphtho[1,2-b]pyran and Its Photodimers.
A 2H-naphtho[1,2-b]pyran, prepared by dimerization of 2-bromo-3-methyl-1,4-naphthoquinone and O-methylation, readily undergoes solid-state [2 + 2] photodimerization to give a photodimer in excellent yield and with excellent selectivity. Retro [2 + 2] cycloaddition can be achieved by irradiation of a solution of the photodimer in chloroform. Interestingly, the 2H-naphtho[1,2-b]pyran dimerizes with a skeletal rearrangement to afford 2,5-dihydro-1-benzoxepin dimers upon irradiation in methanol or via irradiation with hexamethylditin. Furthermore, treatment of the resulting dimers with triethylamine regenerates the 2H-naphtho[1,2-b]pyran monomer. Significant differences in the color, fluorescence, and cytotoxic properties of the monomer and dimers were observed.
†Graduate School for Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Shimogamo Hangi-cho, Sakyo-ku, Kyoto 606-8522, Japan.
Motohiro
M
Ota
‡Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Takahiro
T
Sasamori
‡Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Norihiro
N
Tokitoh
§Laboratory of Food and Nutritional Sciences, Faculty of Nutrition, Kobe Gakuin University, Nishi-ku, Kobe, Hyogo 651-2180, Japan.|∥Cooperative Research Center of Life Sciences, Kobe Gakuin University, Chuo-ku, Kobe, Hyogo 651-8586, Japan.
Takefumi
T
Onodera
§Laboratory of Food and Nutritional Sciences, Faculty of Nutrition, Kobe Gakuin University, Nishi-ku, Kobe, Hyogo 651-2180, Japan.|∥Cooperative Research Center of Life Sciences, Kobe Gakuin University, Chuo-ku, Kobe, Hyogo 651-8586, Japan.
Yoshiyuki
Y
Mizushina
†Graduate School for Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Shimogamo Hangi-cho, Sakyo-ku, Kyoto 606-8522, Japan.
Kouji
K
Kuramochi
†Graduate School for Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Shimogamo Hangi-cho, Sakyo-ku, Kyoto 606-8522, Japan.
Kazunori
K
Tsubaki
D019281:Dimerization; D009284:Naphthols / Q000138:chemical synthesis* / Q000737:chemistry / Q000633:toxicity; D009285:Naphthoquinones / Q000737:chemistry*; D055668:Photochemical Processes; D011714:Pyrans / Q000138:chemical synthesis* / Q000737:chemistry / Q000633:toxicity
C556339:2-bromo-3-methyl-1,4-naphthoquinone; C000605069:2H-naphtho(1,2-b)pyran; D009284:Naphthols; D009285:Naphthoquinones; D011714:Pyrans