抄録
Thymine derivatives having long alkyl chain showed a very high photoreactivity in a single crystal and gave only one isomer of photodimer while the photodimerization in solution gave the four isomers. The crystal structure determined by X-ray diffraction method suggested the formation of the trans-syn or cis-anti photodimer. The photodimer obtained, however, was identified as the trans-anti isomer from the NMR spectrum. It was concluded that the trans-anti photodimer was formed by disrotatory motion of the thymine in the crystal.
