trans-syn Photodimer of polyoxyethylene bisthymine (1) [1,1′-(ethylenedioxydiethylene)dithymine], trans-syn-1,8-(ethylenedioxyethylene)hexahydro-4a,4b-dimethylcyclobuta[1,2-d:4,3-d′]dipyrimidine-2,4,5,7(3H,6H)-tetrone (2), C16H22N4O6, Mr
= 366.4, triclinic P\bar 1}, a = 7.900 (4), b = 10.061 (8), c = 12.048 (4) Å, α = 71.37 (5), β = 78.13 (13), γ = 72.17 (5)°, V = 857.7 (9) Å3, Z = 2, Dx
= 1.418 g cm−3, μ = 0.103 mm−1, F(000) = 388, R = 0.0953 for 1482 observed reflections; 1,1′-(1,2-phenylenedioxydiethylene)dithymine (3), C20H22N4O6, Mr
= 414.4, triclinic, P\bar 1}, a = 8.558 (2), b = 11.077 (2), c = 11.437 (3) Å, α = 108.57 (2), β = 94.37 (2), γ = 99.77 (2)°, V = 1003.1 (4) Å3, Z = 2, Dx
= 1.377 g cm−3, μ = 0.096 mm−1, F(000) = 436, R = 0.0443 for all reflections; trans-syn photodimer of (3), 1,8-(1,2-phenylenedioxydiethylene)hexahydro-4a,4b-dimethylcyclobuta[1,2-d:4,3-d′]dipyrimidine-2,4,5,7(3H,6H)-tetrone (4), C20H22N4O6, Mr
= 414.4, monoclinic, P21/n, a = 10.357 (4), b = 14.578 (5), c = 12.676 (2) Å, β = 97.99 (3)°, V = 1895 (1) Å3, Z = 4, Dx
= 1.453 g cm−3, μ = 0.102 mm−1, F(000) = 872, R = 0.0628 for 1077 observed reflections. The bisthymines (1) and (3) on photodimerization produce cyclobutane-linked trans-syn thymine dimers as the exclusive products. The planar thymines stack one above the other in (1), while they are approximately perpendicular in (3). Planarities of the thymines are altered on photodimerization. The stereochemistry around the cyclobutane ring in photoproducts (2) and (4) is highly strained. The distortions in the bond lengths and angles due to this strain are concentrated mainly on the C5 and C6 atoms, which form the interpyramidal bonds. This strain is comparatively less in the rigid catechol-linked dimer (4). The N3 atom of thymines forms hydrogen bonds in all structures. Photoproducts show closer packing compared with the parent compounds.
反式-合成聚氧乙烯双胸腺嘧啶光二聚体 (1) [1,1′-(亚乙二氧基二乙撑基)二胸腺嘧啶],反式-合成-1,8-(亚乙二氧基乙撑基)六氢-4a,4b-二甲基环丁并[1,2-d:4,3-d′]二嘧啶-2,4,5,7(3H,6H)-四酮 (2),C16H22N4O6,Mr
= 366.4,三菱 P\bar 1},a = 7.900 (4),b = 10.061 (8),c = 12.048 (4) Å,α = 71.37 (5),β = 78.13 (13),γ = 72.17 (5)°,V = 857.7 (9) Å3,Z = 2,Dx
= 1.418 g cm-3,μ = 0.103 mm-1,F(000) = 388,1482 个观察到的反射的 R = 0.0953;1,1′-(1,2-亚苯基二氧二乙撑)二硫杂环胺 (3),C20H22N4O6,Mr
= 414.4,三菱形,P/bar 1},a = 8.558 (2),b = 11.077 (2),c = 11.437 (3) Å,α = 108.57 (2),β = 94.37 (2),γ = 99.77 (2)°,V = 1003.1 (4) Å3,Z = 2,Dx
= 1.377 g cm-3,μ = 0.096 mm-1,F(000) = 436,R = 0.0443 for all reflections; trans-syn photodimer of (3), 1,8-(1,2-phenylenedioxydiethylene)hexahydro-4a,4b-dimethylcyclobuta[1,2-d:4,3-d′]dipyrimidine-2,4,5,7(3H,6H)-tetrone (4), C20H22N4O6, Mr.
= 414.4,单斜,P21/n,a = 10.357 (4),b = 14.578 (5),c = 12.676 (2)埃,β = 97.99 (3)°,V = 1895 (1) Å3,Z = 4,Dx
= 1.453 g cm-3,μ = 0.102 mm-1,F(000) = 872,1077 个观察到的反射的 R = 0.0628。双胸腺嘧啶(1)和(3)在光二聚化过程中产生的环丁烷连接反式-合成胸腺嘧啶二聚体是唯一的产物。在(1)中,平面的胸腺嘧啶一个叠在另一个上面,而在(3)中,它们近似垂直。胸腺嘧啶的平面度在光二聚化过程中会发生改变。光反应产物(2)和(4)中环丁烷环周围的立体化学结构高度紧张。这种应变导致的键长和键角的变形主要集中在形成斜方间键的 C5 和 C6 原子上。这种应变在刚性儿茶酚连接二聚体 (4) 中相对较小。甲状腺素的 N3 原子在所有结构中都形成氢键。与母体化合物相比,光反应产物的堆积更为紧密。