Increasing evidences have implicated that sigma-2 receptor is a biomarker and significantly over-expressed in many proliferative cancer cells with no or low expression in normal cells. Sigma-2 receptor selective ligands have been successfully used as valuable tools to study its pharmacological functions, tumor imaging, and cancer therapeutics or adjuvants. 6,7-Dimethoxy-1,2,3,4-tetrahydroisoquinolinylalkyl benzamides are among a few categories of structures that have demonstrated high affinities and selectivities for sigma-2 receptor and been used extensively as study tools in various tumor imaging and therapy. As a continuous effort, we have synthesized a new series of 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives and evaluated their affinities for both sigma-1 and sigma-2 receptors. Most of these newly developed analogs showed good to excellent binding affinities for sigma-2 receptor with no or low affinities for sigma-1 receptor. In particular, compounds 3b, 3e, 4b, and 4e demonstrated K_i values of 5–6 nM affinities and excellent selectivities for sigma-2 receptor. In addition, these analogs also demonstrated moderate anticancer activities against human liver Huh-7 tumor cells and human esophagus KYSE-140 cancer cells. But their cytotoxicities seem not to be correlated with their sigma-2 receptor affinities.

越来越多的证据表明，sigma-2受体是一种生物标志物，在许多增殖性癌细胞中明显过量表达，而在正常细胞中则没有表达或表达很低。Sigma-2受体选择性配体已成功地用作研究其药理功能，肿瘤成像以及癌症治疗剂或佐剂的有价值的工具。6,7-二甲氧基-1,2,3,4-四氢异喹啉基烷基苯甲酰胺属于几类结构，对sigma-2受体显示出高亲和力和选择性，并已广泛用作各种肿瘤成像和治疗的研究工具。经过不断的努力，我们合成了一系列新的6,7-二甲氧基-1,2,3,4-四氢异喹啉衍生物，并评估了它们对sigma-1和sigma-2受体的亲和力。这些新近开发的类似物大多数对sigma-2受体表现出良好至极好的结合亲和力，而对sigma-1受体则没有或具有低亲和力。特别是化合物3b，3e，4b和4e展示了5-6 nM亲和力的K _i值和对sigma-2受体的出色选择性。此外，这些类似物还显示出对人肝Huh-7肿瘤细胞和人食道KYSE-140癌细胞的中等抗癌活性。但是它们的细胞毒性似乎与它们的sigma-2受体亲和力无关。