Thio- and aminocaffeine analogues as inhibitors of human monoamine oxidase
作者:Hermanus P. Booysen、Christina Moraal、Gisella Terre’Blanche、Anél Petzer、Jacobus J. Bergh、Jacobus P. Petzer
DOI:10.1016/j.bmc.2011.10.036
日期:2011.12
In a recent study it was shown that 8-benzyloxycaffeine analogues act as potent reversible inhibitors of human monoamine oxidase (MAO) A and B. Although the benzyloxy side chain appears to be particularly favorable for enhancing the MAO inhibition potency of caffeine, a variety of other C8 oxy substituents of caffeine also lead to potent MAO inhibition. In an attempt to discover additional C8 substituents of caffeine that lead to potent MAO inhibition and to explore the importance of the ether oxygen for the MAO inhibition properties of C8 oxy-substituted caffeines, a series of 8-sulfanyl-and 8-aminocaffeine analogues were synthesized and their human MAO-A and -B inhibition potencies were compared to those of the 8-oxycaffeines. The results document that the sulfanylcaffeine analogues are reversible competitive MAO-B inhibitors with potencies comparable to those of the oxycaffeines. The most potent inhibitor, 8-[(4-bromophenyl)methyl]sulfanyl}caffeine, exhibited an IC50 value of 0.167 mu M towards MAO-B. While the sulfanylcaffeine analogues also exhibit affinities for MAO-A, they display in general a high degree of MAO-B selectivity. The aminocaffeine analogues, in contrast, proved to be weak MAO inhibitors with a number of analogues exhibiting no binding to the MAO-A and -B isozymes. The results of this study are discussed with reference to possible binding orientations of selected caffeine analogues within the active site cavities of MAO-A and -B. MAO-B selective sulfanylcaffeine derived inhibitors may act as lead compounds for the design of antiparkinsonian therapies. (C) 2011 Elsevier Ltd. All rights reserved.
Copper-catalyzed direct thiolation of xanthines and related heterocycles with disulfides
作者:Zuying He、Fang Luo、Yinglong Li、Gangguo Zhu
DOI:10.1016/j.tetlet.2013.08.097
日期:2013.10
A novel copper-catalyzed, base-free direct thiolation of xanthines and related heterocycles is described, featuring the use of inexpensive Cu(OAc)2·H2O as the catalyst, O2 as a clean and cheap oxidant, and easy-to-handle disulfides as the thiolation reagents. It works well for both aryl and alkyl disulfides. Moreover, the resultant products can be converted into 8-(hetero)aryl- or alkenyl-substituted