title: Synthesis and photocyclization of alpha-methylene-gamma-butyrolactone-thymine heterodimers.
abstract: Two alpha-methylene-gamma-butyrolactone--thymine heterodimers 6 and 7 with 5 and 10 carbon alkyl chains, respectively, were prepared to study the photoreactivity of lactone rings toward thymine and the influence of spacer length on photoadduct geometry. Deoxygenated solutions (10(-3) M) of heterodimers 6 and 7 were irradiated at 365 nm in acetone. Irradiation of compound 6 (5 carbons alkyl chain) gave a single photoadduct 8 (70% yield), while irradiation of compound 7 (10 carbons alkyl chain) gave two photoadducts 9a and 9b in a 3/2 ratio (95% yield). Compound 8 was identified as a cis-syn-endo intramolecular [2 + 2] photoadduct involving the 5",6" double bond of the thymine moiety and the 3,6 exomethylenic group of the lactone. Compound 9a was identified as a cis-syn-exo intramolecular [2 + 2] photoadduct involving the 5",6" double bond of the thymine moiety and the 3,6 exomethylenic group of the lactone, and compound 9b as the corresponding cis-syn-endo intramolecular [2 + 2] photoadduct.
authors.affiliation: Laboratoire de Dermatochimie associé au CNRS, Université Louis Pasteur, CHU, Strasbourg, France.
authors.forename: E
authors.initials: E
authors.lastname: Gimenez-Arnau
authors.forename: S
authors.initials: S
authors.lastname: Mabic
authors.forename: J P
authors.initials: JP
authors.lastname: Lepoittevin
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000737:chemistry; D010777:Photochemistry; D013941:Thymine / Q000737:chemistry*
chemical_list: C014096:alpha-methylene gamma-butyrolactone; D015107:4-Butyrolactone; D013941:Thymine