Hunt W E, Schwalbe C H, Bird K, Mallinson P D
Biochem J. 1980 May 1;187(2):533-6. doi: 10.1042/bj1870533.
In the common dihydrofolate reductase inhibitors an amino substituent replaces the pteridine carbonyl oxygen atom of folates, with altered hydrogen-bonding properties and size. Flexibility in the amino groups could facilitate enzyme binding. Studies of cycloguanil hydrochloride by neutron diffraction show both in-plane and out-of-plane deformation of amino groups. Molecular-orbital calculations ab initio on 2,4-diamino-5-methylpyrimidinium cation confirm that the 4-amino group is readily deformable. The 2,4-diaminoquinazoline structure is reported. Atomic co-ordinates, thermal parameters, bond distances and bond angles for cycloguanil and 2,4-diaminoquinazoline have been deposited as Supplementary Publication SUP 50108 (13 pages) at the British Library Lending Division, Boston Spa. Wetherby, West Yorkshire LS23, 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1978) 169, 5.
在常见的二氢叶酸还原酶抑制剂中，一个氨基取代了叶酸中蝶啶羰基氧原子，氢键性质和大小发生改变。氨基的灵活性有助于与酶结合。通过中子衍射对盐酸环氯胍的研究表明，氨基存在面内和面外变形。对2,4-二氨基-5-甲基嘧啶鎓阳离子进行的从头算分子轨道计算证实，4-氨基易于变形。报道了2,4-二氨基喹唑啉结构。环氯胍和2,4-二氨基喹唑啉的原子坐标、热参数、键长和键角已作为补充出版物SUP 50108（13页）存放在英国西约克郡韦瑟比波士顿温泉市英国国家图书馆出借部，邮编LS23 7BQ，可按《生物化学杂志》（1978年）第169卷第5期所示条件从该处获取复印件。
